If I were you, I would not waste my time trying to find an old MT1D, unless I was doing a 100% correct restoration. They are old, and many times worn out.
Dennis Carpenter Cushman makes an MT replacement carburetor that looks exactly like a Tillotson MT1D. The main nozzle in the replacement only has 2 holes, whereas the original had 4. I have drilled 2 additional holes in two of the Carpenter replacements that I have used, and did nothing to another one. I couldn't notice a difference whatsoever. Wayne has told me he has also done both, and he didn't really notice a difference either.
These carbs are available direct from Carpenter, but if you order other parts from Wayne. I would just buy it from him and save the shipping. Carpenter has a high shipping charge, even if you only order a gasket set!