Yup typically the water pump will be right next to the tank. In addition the tank usually isn't that far from the filler so start on the outside: Where is the tank fill? Go inside and look near where the fill is on the outside? Is that near the bed--look under it? Is there a panel close to there held on with only a couple of screws? Remove it and look.
Many times the pump will be hidden behind panels--don't be afraid to take something apart. If a panel or cabinet bottom is only held on with screws it is made to be removed (if it wasn't made to be removed it would be stapled together). Check under a dinette seat, under the couch, etc.