I'm not talking about cutting down a bayonet into a fighting knife, I mean updating the locking mechanism to allow an older bayonet to mount to a modern M-16 type lug. I think a 1903 style bayonet on the end of a Mossberg 590 would look pretty sweet, but the old bayonets aren't able to attach to a modern lug from what I can tell.
I've found this company that says they can perform this on "almost any bayonet" but $450 seemed hefty for what essentially amounts to a gimmick.