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These are big enough for Yamaha...to replace missing/damaged one on the "fesshunul" models, or to swap fake-for-real on the cheaper (pre-all-brass version) larger buttons.

https://www.riogrande.com/product/White ... chon/87014

while-posting EDIT:

I may have also found the 22mm (European) huge/York-knock-off size here:

http://mopsupplies.mobile034.com/p/9257 ... x13mm.html

...and they also seem to offer the 19mm:

http://mopsupplies.mobile034.com/p/9243 ... x13mm.html

...and 18mm:

http://mopsupplies.mobile034.com/p/9351 ... -13mm.html

...and THICKER 20mm:

http://mopsupplies.mobile034.com/p/9144 ... x25mm.html

I just don't see any musical instrument supplies/parts-related vendors offering stuff like this.

Yep, they are a great resource, I’ve used them a few times; a bit slow, but it’s a long way from Australia. (I ordered a mess of them for a bunch of pearl-less used Conn-Selmer large buttons I got a few years ago).

The only issue I had with them (the 20 mm pearls) is that they are too thick to fit flush in the button (usually around half the thickness they sell, I’ve found around 1mm +/- fits right). I just grind them down to size (wearing a mask, of course ).

It’s a tedious process, as MOP can be quite tough.

I’ll bet that whoever supplies them (maybe Voigt?) to Melton/Meinl Weston/B&S/Buffet/Besson (did I leave anyone out?) would also be a good source……?