I found this video that may help. What the person is calling the water modulator is what I called the fresh water valve in my earlier post. The leak on your toilet may be coming from the water modulator or it may be coming from the hose that connects to it. That's the translucent hose connected to the top right of the modulator in the video. Your RV toilet may be different than this one, but most of them work on the same principle.
Chances are that you will need to remove the toilet to access the valve. It should be easy to remove by undoing the bolts that hold it down and disconnecting the fresh (potable) water tubing that goes to the toilet. Make sure that the trailer water pump is turned off and the city water is not connected. Flush the toilet to relieve the water pressure.
Once off it may be advisable to replace the blade seal in the flush mechanism.