I'm trying to determine what are the most widely used/available cassettes and corresponding cogs. I don't care much whether they are high-end components or low, though I expect the low-end ones to be most widely available since they will be found on low-end production bikes sold in the thousands. Durability is of greatest concern to me, with things like weight being a decidedly secondary factor. The chains in use on the wanted cogs will be 3/32.
Background on my question. I know how these cassettes are constructed and have taken them apart, having done quite a lot of bicycle mechanicing in my lengthy bicycling career (of over 50 years). I also know the economics of buying full cassettes as opposed single cogs: I'm prepared, if economic concerns so dictate, to buy whole cassettes to get just the cog I need from each one, though I don't like the idea of just chucking the rest of the cassette into the garbage.
I have a very specialized project for which I will need a reliable source for cogs for some years to come. The project involves further modifying the complex drivetrain of my custom-built recumbent tandem trike (delta). My idea for the modification will involve using single cogs at either end of the jackshaft on this bike, in place of the cassette/freewheel that are now attached there. The gearing will instead be moved to the rear drive wheel, possibly to an IGH hub like a Rohloff (the only IGH hub, it seems, rated for tandem use). The cogs I will be needing will probably be in the 22-26 tooth range, though I still need to do some more detailed calculating to determine what size will be optimal for this project. Obviously, I will be needing to replace those cogs periodically over the bike's lifetime, so having a ready supply for some time to come will be important.
Input on widely available cassettes/cogs (brands, models) will be appreciated.
P.S. I need the cogs to be completely flat to attach them in the manner I'm envisioning (they will bolt on rather than sliding over a splined central cylinder), so I'm ruling out freewheel cogs, which have a bit of a lip around the threaded hole via which they attach to the freewheel body. I'm located in the U.S., btw.