Hey! I was thinking of replying to this one, but it slipped. I was in the same position as you, initially. I tried to find good places to source bits for the makita collets (6mm and 8mm). But to me, it seemed like the selection was poorer, and the mills very expensive compared to the 3.175mm (1/8") ones. So first I got an adapter from 6mm to 3.175, but they wobbled and was hard to keep properly in place. (the bits sometimes got stuck in the piece)
Soo - in the end I settled for something like this: 1/8" Collet for Makita Trim Routers and haven’t looked back since! I only use the 6/8mm collets for heavy material removal, the rest is done with 1/8" bits now.