I would probably start with Jayco or your dealership to get the correct one. They may have it available from parts. There are several options on eBay right now as well, but that could be a bit risky if you order the wrong one.
Check to make sure your awning is prepped for the room. There should be strips of Velcro or zippers around the underside of the awning flaps, our 1007 was Velcro, but I know Jayco changes parts suppliers from time to time. The Dometic awning/rooms look like they use zippers. Know which one you have.
One last word of advice is, be sure you really want to use it. In 8 years of ownership, we used ours 2 or 3 times only. It closes in the trailer quite a bit and it is a bit heavy to carry around all that time if you aren't going to use it. Mostly we just hung a small tarp across one end of the awning for privacy. We also have a Coleman Casa Loma 15*15 All Day Dome that we use for additional shelter that is much more versatile. Also note that we camp in a zone where the mosquitos are the size of Mac trucks (the horse and deer flies are made by Sikorsky); we quickly learned that screened rooms serve more to keep the trapped bugs (and birds and bats) inside than to keep them out.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2012 Chev Traverse LT with TP