Long post from a guy who has played guitar since 1975, almost fifty years, including all sorts of generations of acoustic guitar pickups.
Current standard technology is to install a piezo bar underneath the bridge saddle. On one of my acoustic guitars that did not have a system when first purchased, I did just that: made sure the bottom of the channel was flat, drilled the little hole at the end of the bridge saddle channel, installed the saddle pickup, installed the controls on the side of the upper bout, and installed a battery box. Yes, I laid the template on the side of the upper bout and hand cut it out myself with a tool that was essentially a sabre saw blade installed in a small wood handle. You can't tell the guitar came any other way. Yes, it is invasive. but the upside is that: 1) you have good tone 2) you don't have to always be removing/reinstalling any other pickup system and risk fouling up either the system or the guitar, 3) it is plug-and-play with immediate control of the tone and volume on the guitar, and 4) you are not limited in your choice of strings as you are with "electric" pickups. The battery box needs to be accessible from the outside instead of the prior standard of a little pouch affixed to the inside of the heel block, so you don't have to loosen strings every time you change a battery. That may be especially important on a 12-string due to the added tension and the inherent flexing of the neck every time a battery is changed. Best of all, a good setup does not affect the tone of the guitar when played acoustically.
I have played both the Fishman and the L.R. Baggs on stage with different guitars, both to good effect. The system I installed is a Fishman. My Gibson J-45 came stock with an L.R. Baggs. My Ibanez 12-string came with its own version stock, and it is alright. These systems are so much easier than they were a generation ago because of the plug-and-play aspect once installed, and some even have built-in tuners. I recommend a system like that, with a built-in tuner, highly for an acoustic 12-string, as on my Ibanez, for obvious reasons.
If the stage volume gets up there in level, you might need a rubber soundhole plug to reduce feedback. I have one for each of my acoustic guitars that I keep in their respective cases.
Fishman & L.R. Baggs are the best piezo systems for straightforward saddle pickups. There are some piezos wired directly to an output jack, but unless you have a separate external preamp, you do need an on-board pre-amp with a piezo due to the ultra-high impedance and low output of the crystal. L.R. Baggs makes a control unit that mounts in the soundhole. That sounds inviting, but I don't like this type of control because you are still fiddling with the soundhole, still have to figure out the battery, and a soundhole control precludes using a soundhole plug onstage unless you modify it for access, which defeats the purpose.
If you want a removable pickup like the OP's father had, There are several soundhole pickups now available from various manufacturers, including Seymour Duncan, DiMarzio, and Fishman, among others. The Fishman pickups are semi-permanent, having set screws to secure the pickup in the soundhole. This defeats the purpose of having it removable, although they are so slender that sound is not significantly compromised. Just like any other "electric" pickup, I recommend a humbucking version for the lower noise floor. Moreover, since they are essentially electric guitar pickups, you might have to use "electric" strings instead of your favorite bronze. Martin Monel strings would work well for this setup.
Other systems: on the low-cost end, stick-on piezo pickup "dots" still have their advocates, but there are much better systems out there. You don't want the adhesive to let go in the middle of a gig. If you want to get high-cost esoteric, there are systems that actually mount a condenser microphone inside the guitar, or a combination of pickup & microphone, claiming a more "natural" sound.
Sweetwater has one of the most extensive selections of acoustic guitar pickups:
https://www.sweetwater.com/c985--Acoust ... ups?pn=all
and
Here is a review of various pickup system types on Reverb:
https://reverb.com/guide/buying-guide-acoustic-pickups
If you don't want to install it yourself, find a good acoustic guitar shop that has a good luthier who will install it as part of the purchase price.
Of course, for "natural" sound, nothing beats a Sennheiser professional external condenser microphone, but unless you are in a studio, it is overkill. The few times I played this setup, the sound engineer took more time to place the microphone than the time it took laying down the track, and I was tense about moving the guitar even the slightest little bit off-axis and ruining the track.
Bottom line: unless your guitar is a collectible, like, say, a pre-war Martin, and if you are a plug-and-play guy, I recommend for 99% of players, including all occasional players, install either a Fishman or an L.R. Baggs system for their overall tone and ease of use.