[ByronRACE]

You already know the bore of the master cylinder is .750" and the outside diameter is 1.125". Which means your wall is 0.1875"

And, you know that a 1.0625" cylinder fits.

So, why not flat file .07" off the problematic side of the new clutch master cylinder leaving you with a .1175 wall; which is plenty heavy considering this is just a clutch; which is a relatively low pressure application and can tolerate the worst-case unlikely event of a cylinder failure.

In my opinion this is an extremely safe experiment, and far easier than trying to shop for a thin-wall part that may not exist.