My 2015 Jayco came with a Cavagna regulator. This was the cover:
RV Propane Regulator Cover White Plastic Cavagna Group 21-1-110-0161B | eBay
After buying the trailer I immediately ordered a spare. As luck would have it the regulator crapped out just last month and needed to be replaced. Unfortunately, when I threw out the old part, the 2 covers went in the trash too, or I would send it to you.
I believe Cavagna will indeed sell the single part. Call them directly, forget about the distributor.
I do about 95 / 5 shopping with EBay / Amazon. The latter usually charges shipping unless your order is over $50, and almost always charges tax. EBay is usually free ship, no tax. In any event, the cheaper one gets my order...