If you strike-out locally (USA vendors), perhaps check-out Wasp suspension parts out of Australia, as the upper bump stops I'm going to be using have the square base:
However, the lowers don't seem to have this:
Full disclosure: The Australian A-body I'm working on is not my car, but it came with a full front-end rebuild kit, all in boxes, in the trunk. I don't know how old the kit is/was, and the vehicle owner isn't available, but maybe they are still available this way Down Under.