900 Thunderbird Brakes And Rear Wheel

If I remember correctly the brake calibers are made by tokico and rebranded as triumph so there may well be a few off different bikes that would be suitable but not heard of any one doing it.
Have you bled and replaced the seals?
A caliper refurb May be all you need with fresh pads. Before spending massive amounts of money on replacing calipers try that.
As to the rear wheel no idea but you never know some one else might have

 

When you say shocking! What exactly do you mean? Lack of efficiency? Too much lever travel? Brake fade? No bite? There are something's you can do depends what you want. Age of bike? Miles? Have attempted any refurb?

 

street triple fronts will go on

 

Cheers for that DD wasn’t 100% sure if they were Nissin or Tokico.

 

Rather than buy pattern brake parts I always prefer to buy genuine Nissin brake parts. The best way is to buy genuine but from Honda. The 27mm dia piston calipers are a common part but I just quote from a ST110 0Pan European front. btw the rubber boots are the same too.
https://www.fowlersparts.co.uk/parts/5000129/st1100pt-1996-e-mkh/front-brake-caliper