I have started using two belts. The first is a leather strap like I use for the sporran. This keeps the kilt tight and in place. The second is a larger belt that I can attach items to. The second belt can be anything from a renn-fair belt to a 4-6" wide. It can also be removed and/or replaced and not allow the kilt to become unbelted.

Remember an unbelted kilt can be an embarisment for those around you.