Spurred on by BB's timely reminder, My rear caliper was really sticky and as I was in Bristol today popped into Fowlers to get a caliper kit, forgot the OE Triumph ones dont come with the slide pin boots, and in fact Triumph dont even list them. Lucky for me I got an on the ball parts man who looked up the Honda equivalent.
Honda Part nos, 45133-MA3-006 (Large One) 45132-166-016 (Small one), about £7 the pair so not particularly cheap but might get you out of trouble if you cant find anything else.
Rear caliper stripped and rebuilt and no longer dragging, luvly jubbly