Recycling center sometimes has a big enough scale.
If you want it perfectly accurate unhook from tow vehicle all on one scale. Remember the registration $ goes by weight so you are paying for what you use in theory. So leaving it hooked up would take out the tongue weight.... $$
there is a recycling place in Santa Fe 13319 FM1764, Santa Fe, TX 77510 off of 1764 between 646 and hwy 6 (across the street from the new tractor supply) they had a scale and might still. i weighed a few trailers there back in the '90s