you want pbt or abs first?
abs <50 before postage can settle maybe 

Depend on material, if blank (and black or white color), normally below RM50 for a set.

For blank PBT (color?), you can opt for imsto and keycool, both from taobao.

Nyan cat on taobao,
http://item.taobao.com/item.htm?spm=a1z10....&id=20549639129
He got light blue PBT, but dye-subbed. I think you need to special contact him to get blank one.

BTW, just FYI, PBT rarely had black color (the dark grey PBT of Vortex is among the only few I came across). Thats why they (manufacturers) normally always use POM for black, PBT for white.
If you do consider POM, then Keycool got them.
http://item.taobao.com/item.htm?spm=a1z10....id=14011959835&

Apart from black POM, you can also opt for rainbow POM.
http://item.taobao.com/item.htm?spm=a230r....&id=10750871018

Nope, they are a little coarser than normal ABS, but extremely fine and nice to type on.

Apart from black POM, you can also opt for rainbow POM.
http://item.taobao.com/item.htm?spm=a230r....&id=10750871018

I think it's the Ducky's cherry stabilisers problem 
My backspace had that problem as well.
Other board was fine.
I guess the only way is to just use them until it gets looser.
anyways, where did you get those keycaps ? looks really good 

Oh god, I think I warned that Pom is dangerous for blue switch b4. Removing Pom from blue really require some suitable tools, skills and carefulness.

Btw, don't try to force the keys back into the switches especially for blue switch, you gonna desolder and disassemble the switch 1st to put it back.