imsto has nice looking caps ready to go that it seems he could probably run in quantity. check out his taobao for the varieties he has already in production. note that imsto's caps are dyesub PBT, and in particular he has access to high quality cap molds that are preferred by some on the forum for the amount of material used per cap.
getting caps from SP is very time and labor intensive. the product is high quality once they have production down exactly, but hit or miss before then due to misunderstandings/QC issues/etc. if you put more capital into production, this may be different for you, but for our smaller production runs, it's a longstanding problem. eventually they give us very high quality product, but there are often bugs along the way. unfortunately, they are the only game in town for doubleshot caps.
the korean boards at kbdmania and OTD have either run group buys or paid directly for production of some very nice looking caps from SP. sherryton is importing some of these caps into the US, but there may be more opportunities available.
imo, no need to reinvent the wheel. the ability to get one of the nicer looking for less imported cap sets into the US, or the ability to stock nicer doubleshot caps with no lead-time should cost you less and give you a bigger return in a short-run than trying to source and design your own.
re: wasd and qwerkeys. wasd seems to get their keys from the same factory that ducky, costar, and imsto get theirs. qwerkeys gets their caps from devlin in the UK. the usual suspects around here are not that into devlin caps.
