I have one of the 5.11 Trainer Belts.  I like this belt.  I like the way it adjusts and the velcro to control the tail end.  It is stiff enough to carry a full size holstered handgun comfortably.  My problem is I go through a metal detector at work frequently and the large stainless steel buckled causes issues.  It is also pretty heavy and I never plan to hang from the buckle so the stainless buckle is a bit overkill for my use.

So is there a similar configured belt that used a plastic buckle?  Any recommendation would be appreciated.

5.11 with plastic buckle

I also wear a nylon 5.11 with the plastic buckle daily. Stiff enough for a G19 carried AIWB, but not so stiff that it still doesn't conform to your body around the hips. I have one or two stiffer nylon belts that really dig in uncomfortably around the hips because they are so stiff.