Be careful if you're thinking a simple conversion will do it: converting a deb to an RPM and vice versa, due to vast differences in filesystem layout, is like dressing up an American in French clothing and expecting him to fit in. Differences in filesystem layout, kernel, libraries and tunings are like cultural differences; and you can't expect a smooth fit AT ALL.
FPM is great if you never ever want to package something properly, just need a payload delivery method and also don't mind never getting a source RPM. Since FPM packages something after it's spraypainted onto the filesystem (make install or similar pre-2000 methods of 'installation'), you're also not packaging in a clean isolated location with all the intrinsic benefits.
Ultimately, you will save a small amount of time and understand a lot more about the process, methods and logic if you just package it. The 'small' amount of time is like the difference between 90 days and 91, but the 'day two' problem after delivery, where small changes need to be made due to unforeseen problems in delivery, is solved trivially.
Before you consider fpm or other hacks, if you can't/won't learn to package on enterprise linux, just hire someone. The right nerd will do it properly, and while you won't know how or why something was done a certain way at least you'll have the SPEC files to tune quickly.