You can buy thermometers with probes at Wal Mart for sure, that is where I got both of mine, cost was 10 bucks for the first one, and 15 for the second one I just recently got.
Mirage came out of brumation on April 26. He was doing great. On May 2 he started acting funny. We just redid his tank, and he keeps going into one of his hides. He just lays there. He shows no intrest in food. HELP!