The only SS belt bikes I know of are built by Spot as SS XC bikes. There's only one length belt, so the gearing options are few because whatever size the 2 rings are, they have to add up to the same length. There's enough adjustment in the rear dropouts to alter the rear cog by maybe 1 tooth. I'd look to them to see what components they use for hub and crankset. Googling for SS belt bikes, one gets mostly SS internal hub bikes, not much help there.
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