You'd either have to weld center stand brackets to the frame or get a frame from a later 750 Twin. The diagrams at partzilla show that the 83-84 K1/K2 Ltd Belt models had a center stand. Those frames are probably otherwise virtually identical to the 750-CSR. If you go the welding route, then a center stand from a 750K is probably the best match.
For around the garage you could buy or make a portable main stand. Years ago I saw one that was maybe a 2x10 w an iron pipe handle.
You could do an internet image search for homemade motorcycle center stand or something like that. There are probably youtube videos.
