If leather would work check out the beltman belts
http://www.thebeltman.net/nobuckle.htm
I just got off the phone with "the belt man". He was very helpful in answering my questions. I just placed MY order (with a buckle). Here is their number in North Carolina. (919) 387-1997
Everyone has certain makes of belts they like. It really dependents on what works best for you and your budget. Daltech has a velcro one https://www.daltechforce.com/specialty-belts/velcro-no-buckle-bull-hide-bullbelt® My buddy got one because usually belts with buckles dig into his stomach, but this one seems to work well for him.
I really like the Dynamis belt, but it's not incredibly stiff. More of an edc / comfortable setup. I've racked my brain, and can't think of anything that really meets your criteria.