There's a GMK group buy coming up soon from ctrlalt, also feng is about to launch a GMK group buy and Ivan is about to start shipping dolch GMK sets, no doubt some of those will show up in the classifieds.
And as much as I love doubleshot GMK ABS caps, these pbt caps http://www.ebay.com/itm/PBT-Keycap-Set-for-Cherry-MX-based-Leopold-Keyboard-Front-Face-Englih-Black-/281377716241 are some of the best caps I've used and I'm not really the biggest fan of pbt. I recommend these caps to anyone looking for a set of caps to use and for the price they can't be beat.
^^This man speaks the truth. You should be able to find other versions of those Leopold sets on eBay if you don't like front-printed. They're Cherry profile thick PBT and really well made, similar to your Choc Mini keycaps, but in PBT instead of POM.
If you're interested in blank black thick PBT, you may be able to get someone to transfer their set in the Pitch Black GB (although the production schedule on these is still a bit vague): http://geekhack.org/index.php?topic=50935.0
Here's an idea of what the Dolch colour scheme looks like on a KUL ES-87:
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That dolch colour scheme is really nice to be honest, I really need to look into getting me some of those, I really like them.
And as for those Leopold keycaps, they're really nice also, I've never really considered using side printed keycaps, but I will admit, they do look really nice and they're rather cheap also, I might just go ahead and pick some of them up now and just see how they feel and what not. I'm not a huge PBT fan either, but I'll give them a go regardless.
Edit: Just ordered those keycaps off ebay, they look to be low profile like my Noppoo keys like Oobly suggested, so I just had to have them! Hopefully they will be decent enough to type on, as long as they're better than ABS, I don't really give a fk.