The elaborate way could be to build the RPM from the .src.rpm, unpack it with rpm2cpio and cpio, 'dd' a file the size of a floppy, loopmount it, format it, mount it, copy the installed files to the mounted location, umount, loopmount -d, then 'dd' that image to a floppy, but (all as unprivileged user

installing the .src.rpm should get you the tarball any patches, additional files and the .spec file, running 'rpmbuild' with the "-bi" switch and supplying the /path/to.spec file should configure, patch, build and install the package, then you could copy the installed files to your floppy disk. Seems easier to me.