For used parts from across the country try, car-part.com and partshotlines.com. Search for "Lock Actuator". I found only one listed in my area, but you could also search for front door and then choose electric or auto option. Then call the various yards that get a hit and ask them if they will pull one from a door (some want to keep the doors complete/intact). If you find one,they will ship it to you. They usually warranty items for 30 days or more. Used may not be your your first choice, but it is an option.
P.S. Also, determine whether your rv was built on a 1997 or a 1998 chassis. There were major changes made to the body for 1998 including different front doors (which may or may not use the same actuators).