What you're actually looking for is a router/repeater that is capable of what is called WiFi as WAN which means that it can receive WiFi from a source, such as the RV park, and rebroadcast it inside your RV. Regular home routers don't usually have this function because you're unlikely to "drive" your house to where there's a WiFi to connect to!
There are a number of companies that offer routers with WiFi as WAN capability. You can read about this topic on the Mobile Internet Resource Center website. MIRC is run by good people who aren't affiliated with a specific manufacturer so you get good unbiased information. Some portion of the site is free; some requires a subscription.
MIRCJoel (AKA docj)