Hi Roman,
I have actually asked around quite a few tool places for suitable collets but have had no joy with them, they are happy to sell me a router or die grinder with them but they dont seem to have just the collets.
I dont have a lathe (It's about the only tool I don't have ) Are you interested in turning me out a custom Ozito 6mm collet insert? happy to pay
regards,
Gully