+1 on the Escapees Smart Weigh. They do a very good job. They did ours last year in Livingston.
Recently had our coach weighed at the American Coach Association rally in Yuma, AZ by RV Weigh. Paul & Doris are VERY knowledgeable on the issues we face. They did a great job. Check out their website at RV WEIGH - Mobile Weigh Station
for their list of where they will be. They are base in Henderson, NV but make a lot of the larger rallies out that way.
One of the keys to weighing is to show up loaded as you would normally travel. For us that was full of fuel, 1/4 tank fresh water, empty black tank, and 3/4 tank LPG.