You could always cancel the bag order & just use a bungee cord to keep the lid on & put it inside a garbage bag to & from the campgrounds instead of cleaning the SJ before & after in order to keep the bag clean that you are using to keep the camper clean.
Or, you just could put it in the garbage bag to keep your SJ bag clean, which you are buying to keep the camper clean.
Or, you could clean the SJ before & after, use a bungee cord to keep the lid on, & skip the garbage bag since you cleaned the grill already.
You know, I read that hearing Jackie Gleasons voice.... But I get the point... It's more than cleanliness though. The grill has hard, somewhat damaging surfaces if they get introduced to the vinyl covered engineered wood surfaces in the camper.
FWIW, we are opting for a Eureka SlideInn 8ft box camper (our truck is a 6.5ft bed, which means 18" of the camper will rest on the tailgate). They don't show on their website, but they offer a 48" cabover option, with a pull out for a queen bed. We are working on ordering that. So basicaly an 8' camper with 48" cabover sleeper, A/C, and roof rack. Working with the MFG to see if they can option in hot / cold water system. The options list doesn't show it for this model, our rep is talking to Engineering to see if they can do it... They don't offer any sort of external stowage cubbies. And due to the camper overhanging the tailgate, my old hitch haul isn't really an option...
I have used a Weber Smokey Joe carried in a trash bag in a camper before, LONG time ago, I had a 1964 VW Westfalia camper. The Weber was stowed in a trash bag, and it dented the crap out of the interior wood in travel over rough terrain. I am going with a truck camper instead of a much larger travel trailer because i want to camp where 4x4 is a requirement... (Padre Island National Seashore, Guadalupe Mountains etc...).
The Smokey Joe bag per the mfg description has 5mm foam padding, which is about the same as my cheap gig bags for my basses, and honestly, they give protection to the wood on my musical instruments, it should protect the camper interior...