If you are looking a Taurus thumb piece for a Model 66, Numrich has a stainless version in stock. https://www.gunpartscorp.com/products/582910. If OTOH, you really want to use a S&W thumb piece there are a number of differences with the Taurus. First the Taurus thumb piece is attached with a screw into the bolt, while the S&W attaches with a slotted nut to a threaded stud coming off the bolt, so you would have to use the Taurus bolt when attaching the S&W thumb piece or visa versa. Both makes have slot in the on the side of the gun which allows the thumb piece Further, while most S&W thumb pieces will fit any S&W frame (the same as Taurus), there are different finishes and style (also the same as Taurus). My new model 65 has what is called a kidney shaped thumb piece, but there is also the more symmetrical standard style (S&W also has these two styles).
Hopefully some one will have better specific information on the compatibility.
Thanks and Merry Christmas. Unfortunately, a lot of US suppliers don’t ship to Australia and locally it can be hard to source Taurus gun parts easily. So I have to find equivalents and make it work and S&W parts are available on Brownells or Midway. I’m after a thumbpiece that I want to grind down the “sharp” edge on the top of the thumbpiece because of the way I hold my gun in matches and I don’t want to wreck the original part off the gun.