This. Is. Aggravating.

I have 3/4ths of Gemma's enclosure covered with two towels. I have a 100w ceramic heater on the 1/4th that's not covered. She's got a UTH, two hides on either side, & a bowl of water in the middle of the enclosure. I cannot, for the life of me, keep her warm side temperature in range. That 100w heater is a joke. Her temperature barely stays around 82 with the damn thing on 24/7. I've looked for a higher wattage, but I can't find one above 100. Her UTH is set at 90, & she's got about an inch of substrate under the hide where her UTH is (she doesn't really burrow, but I still check every day to make sure she hasn't reached the bottom). Please, someone give me SOMETHING. I've tried everything I could think of & everything I've read on here, but it's not working. I've almost successfully convinced myself I can get her to wear a body sweater if I can crochet one. HELP.