At least at the local fabric stores here, there are several types of belt buckles that snap into place. They don't have to be sewn, and are fairly secure. Get one of a die-cast type and you have a good throwing weight, too.

There are also ones that are just the loop and pin - thread the pin through a few of the knots and it would be fairly secure.

if you wanted to get fancy, you could 'weave' the buckle into the belt.

Rena