WiFi Extenders that work for public WiFi routers

I have a Linksys WiFi extender that I recently tried to use at an RV park that had WiFi. The WiFi signal was quite weak at our site so I wanted to set up the extender. To login to the public WiFi on my laptop, I would have to open a browser and agree to the terms of the public WiFi in order to connect. When I try to set up the Linksys extender, it will recognize the public WiFi router but will not connect since it can't open the browser to agree to the terms and conditions. Linksys says that I need the IP address of the public WiFi router but no one at the RV park knows what this is. Does anyone know the solution to using a WiFI extender? Are there ones that actually work? I don't want to spend hundreds of dollars and install something like the Winegard Connect 2.0 4G and LTE to the roof.