They fit a regular board just fine. I've personally done it on the keyboard I'm typing this comment on right now.
The problem is there's theoretically more 'wobble' introduced, which honestly is the same amount of wobble with the housings anyway. I didn't notice a difference.
As for OP's question, there's an artisan usually more active on reddit with the name busgamer7394. They have created entire hi-pro artisan sets. They're currently privately selling HHKB sets for $85 with limited availability, and will scale up from there for realforces and fc660c keyboards.