For casual, Eagle Creek used to make a black military web stlye belt, but with a black plastic buckle instead of the brass. Dont know if it's still available.
Magellans has a thin dress type reversible black/brown leather belt with plastic buckle pn MA502. Probably what you're looking for.
Getting rid of my metal belt buckles has got my "false alarms" at the WTMD down to zero. However it is no guarantee you get to always leave your belt on. December in AMS they were running a Belt Fetish operation, ALL belts must come off and go thru the xray. I told them mine was plastic and would not alarm the WTMD, but no exception. Go thru the MD trying to hold your pants up. The joyful experiences of travel.
