This topic came up some months ago. Here's what I did - I had a plastic track loop from a Tamiya M-3 halftrack kit in my spares box. I unlooped it, then cut down the length of the track, separating the two halves. The track is flexible and has small parallel grooves that look kinda like the ammo belts (close enough for my eye, anyway.)
(Yes, I know the seat belt is in the wrong spot....I fixed that after it was pointed out to me earlier....my bad.)