I purchased a 6mm to 1/8" adapter from here (Europe) but I can’t remember where exactly, must have been Amazon or eBay
It worked fine. Later I bought this 1/8" precision collet from Elaire for the Makita router, it’s better
I had to buy from Elaire in the US though, so it was a bit costly and took a while to arrive
Carbide3D sells a nice set of similar precision collets for the CCR (which is very similar to the Makita as I understand) that has a 1/8" collet in the set, but again shipping cost and delays.