[Wlug] RFID reader/writer

Does anyone have a recommendation for a RFID reader/writer for Linux (and Windows if possible)? I'm looking for a relatively inexpensive solution. My kids just got Skylanders Imaginators. I found some code to read the characters. I started thinking about the Game Design merit badge for Cub Scout Webelos. I'm wondering about the viability of building a "portal" device and having the kids make clay figures with rfids inside the base. Obviously the game would be as complex as Skylanders. I'm thinking 2D using pictures of the models.