I have Tokico Calipers and one of the pistons has corroded so that the brake binds on. Tried stripping it down and smoothing it off but no good. Does anyone know if I can get new Tokico Pistons or am I looking at a new Caliper/Piston set up.

Having real bother tracking down Tokico parts in UK - can anyone help please, I don't really want to have to replace both sides with an aftermarket set up if I can avoid it?