Source for replacement knobs for Maccaferri Islander ukes?

I picked up a couple 50s era Islander ukes at an auction the other day. Two of them are in workable shape, but one is missing a couple knobs (the tuner shafts are still there).


I've been googling without any luck--can somebody point me in the direction of a place to buy replacements? I get the idea that those tuners aren't a standard size, although, I haven't confirmed that the knows to my cheapo friction tuners from eBay won't fit, they certainly won't match. That's not the end of the world, but if it's just a matter of spending $5 at the right store online, I'd just as soon get proper knobs.

Any suggestions on where to look? Thanks!