You should be able to go to any AGCO / Massey-Ferguson dealer and either get the part, or order the part. If it is the bracket that holds the lift arms and the drawbar, my 5015 parts book lists it as "BRACKET, lower link, P/N 2101293-5."
I've had a 4WD 5015 for about a year. Although the parts have been a little expensive, I've been able to get everything I've needed from our local ACGO dealer. Parts that were not in stock were ordered by the dealer from a warehouse in Illinois and had them within three days.
If it is a part that has been discontinued, search the forums for places that provide parts for Hinomoto tractors. The Allis 5015 is the US version of the Hinomoto C172 (2wd) or C174 (4wd). It was also sold in the US as a Massey-Ferguson 1010, but color, the front grill, the hood, and the transmission were slightly different.