Frank's garter belt seems to be a basic rectangle, probably decreasing in the center back where it closes. The top and bottom edges probably have some kind of elastic or channel on them, and there seems to be lace over much of the edge - torn off above his front right thigh.
The straps seem two-toned (good luck finding that) with adjustable clips (you can pilfer off a thrift store find) and silver garter clips with white rubber nubbins.
The lace looks quite faded and almost like a charcoal gray next to his black undies. It has a medallion and diamond motif.
