Banggood sells an 84-key set of medium-thick blank white PBT caps for $17.00 and free shipping anywhere in the world, $1.70 if you want tracking. Takes about three weeks for it to get in.
Otherwise, if you have lots of money, you could get the really thick imsto caps from feng on ebay, but they're really overpriced in my opinion, because you can get Vortex double-shot thick PBT keycaps (the only maker I know of besides Deck) for a paltry $33 from the group buy or a little under $40 from MechKB if you live down under.
If you want backlighting, you'd probably be best sticking with Ducky Shine white keycaps, which are laser etched like pretty much all backlit-compatible keycaps.