I still think a .30 Cal can is a good place to start for a general purpose bolt gun can, that's where the largest variety of options are, and they work quite satisfactorily on sub-calibers. Understand you're specifically buying for a 6mm, but if you have rifles in any other sub-.30 cals that you have an inkling that you *might* want to shoot suppressed, I'd go ahead and cover those with a .30 cal, because once you start shooting with cans, you're going to want to get everything threaded.
There's a reason .30 cal cans are so popular, and it's not just that everyone is ignorant of sub-caliber cans. I think I ran various .30 cal cans on pretty much everything from .223 to .30 cal chamberings for a solid decade before getting smaller caliber cans, it works fine for almost all uses, and you can always buy the narrower use case stuff later after your already able to suppress everything.
Anyway, I'd agree with Q_Sertorius's list and there are other good ones too. My latest is an Echo Zulu Altitude .30, and so far it sounds quite good to me on .223, 6mm, 6.5mm, 7mm and .30. My Nomad Ti has long been my go to hunting can, either way you go I'd recommend Ti for minimum weight and hub compatible for maximum flexibility and future mounting options you might one day be interested in.