Try finding a weigh station near you on this link:
Weigh Station Scales Locations in Washington WA
I have a friend that lives in Bandon Oregon and there's a weigh station just south of town on Hwy 101. I've never seen any personnel there, but the weight is displayed on an electronic sign. I've gone there and obtained all the weights you're looking for, and it was free. You might call Washington DOT and see if there's a similar setup in your area.