I've stayed in a number of parks, both state and national where filling an RV's water tank form the hydrant, even with a "water thief" is strongly discouraged, and in some cases, prohibited. The solution to this problem is a couple of 5 gal collapsible camping water jugs. Fill them at the hydrant and bring them back to the RV to fill the tank.
The last time I needed to do this, I connected a water hose to the bathroom sink using a hose adapter I bought at the hardware store. The other end of the hose went to the fresh water tank fill point. I changed the pump intake to the winterize position and stuffed the winterize intake hose into the water jug. Turn on the cold water at the faucet, turn on the pump, and watch the water drain from the jug and go into the fresh tank.
If you have an outside shower, you can do the same thing using that connection instead of the bathroom faucet.
The only caution about doing this is that when you normally de-winterize, you need to make sure you clear out any antifreeze from the hose that feeds the pump. I do this by flushing the antifreeze out with water using the winterizing hookup.