Gok, can you give recommendations for key sets or what to buy extra for, for example GMK or KAT sets? I’m thinking compatibility, not colours.
I understand if that is too much to ask for.
GMK Space keys round 2 will have support for a 3u, 2u, and 1u spacebar in CR, L9, N9, CP, CC, U9 but is split into 3 different kits. Look for sets that use those standard GMK colour codes.
Some examples of these sets are GMK Dolch R5, White on Black, Noire, Olivia, Honeywell, Nines, Skidata, Beta, 9009. There are quite a few others as well.
Along with those colours, sets like Zambumon's Serika 2 has compatibility for it in the Macro Expansion and Spacebar kits.
Aside from GMK, Epbt have had 3u spacebars in their kits for a while and ome sets even have 2x 3u spacebars but they lack a proper convex 2u spacebar (I think they will have moulds of this seen though).