Many people have the same situation, . . . including yours truly. Suede might work, . . . suspenders might work.
Unfortunately, . . . you probably bought a straight belt, . . . which works fine for folks who are not "buttless" so to speak.
A properly curved belt, . . . properly cinched up tight, . . . will not fall down in most of "our" situations.
At your next shoot, . . . look at the rigs folks are wearing, . . . most of the time you won't see the curve when they have it on, . . . but you might ask a few of your pards, . . . try one of theirs if you can find one.
If theirs stays up, . . . you found the problem.
Camano mentioned loops, . . . I don't think there is any "rule" against it in equipment, . . . but if you had someone bend 4 "S" hooks for you to go up and hook in the top on your pants or britches belt, . . . and at the bottom under your gun belt, . . . you would then use two belts to keep everything up. Making them out of black kydex, . . . should be a quick fix, . . . should hold, . . . or you could even go to Tandy and get metal belt keepers and attach them together to do it.
Just remember though, . . . if you do that, . . . and stuff comes down, . . . well.............................
May God bless,
Dwight