28 gauge ammunition is available on just about every site that sells it including Apex, Foxtrot and Rogue.
Loading of your own TSS isn't that technical and will save you $4 a shell. I like to do choke/load pattern work so I enjoy it as well. I will never change my recipe as long as the 18 g/cc TSS is the top ammo to use. Any choke, I love my IC, that patterns well is worth whatever you paid for it. The 28 is also a fabulous field gun and sporting clays/skeet gun. Al Baker