Many of the truck stops have CAT Scales that are installed on a trestle above ground, so you can't run one side onto them. A simple in-ground scale (flat with the adjoining pavement) would be best and that will require calling around.
A Portable Scale would do it. Could be slightly inaccurate in total axle weight since you're weighing a corner that's a little higher than the other, but it'll call out any major differences.
Michelin acknowledges that RV's are often loaded off balance which is why the RV version of their Weight/Pressure Chart uses corners. Still, this is the Gold Standard procedure. You can get very useful information from a CAT Scale. If you tow something, have it hitched up and pull the whole rig on. You'll get Steer (Front of RV), Drive (Rear of RV) and Trailer (Toad, Boat, Trailer, Whatever) and having this is FAR FAR better than no information while you hunt the Perfect Scale. Going CAT Scale fee looks to be $11.00