The version of Ncom I used worked in KS/OS 1.3, but as noted, I used it from a hard drive. With 1 floppy drive, you are not going to have anything but trouble; with enough RAM you can set up a RAD drive and load everything there making it perform like a hard drive.
At this point I would normally be sarcastic and glib, with a comment like, "Simply put, a 5 ounce sparrow cannot carry a 1 pound coconut," but this weeks threads have been about what one CAN do with an A500 -- an A500 AND money! So get out there and spend! Start with a replacement floppy for the one not working...