You may want to get a high powered basking bulb. It'll get your Temps up but kill your humidity. What I did with my ball before I ditched lamp heating was get some eco earth and completely soak it put in your tank then put a dry layer of reptibark on top and it'll retain the water for weeks. Keeping your humidity high.
I keep my ball in a 36×18×18 tank and I read about 55% humidity.