I do not know if that 36014-061 from Z1 Parts will fit. You could ask what the bolt-hole spacing is & the overall length.
The cross-reference at Partzilla for the KZ750-R1 lists a few models that use the same 36014-1061 chain guard, including the 1000J & the KZ1000-P1 Police. ..... Note: some sellers erroneously list the early 1000C Police bikes as P-models, but the two are different & have different chain guards, and I don't know if they're interchangeable.
When considering a non-stock chain guard, something you can do is compare swing arms which might give clues to the bolt hole location & spacing.
1981 KZ650-CSR. Competition, Sports & Road.