Build your own just like these for less than $100. Really super easy to do, and they work GREAT. I've posted pictures of mine on BR before, as have others.
Once again, may I strongly suggest one be very cautious about the temperature range for any device you use. Bowling balls can be very sensitive to that. Most gauges that come with dehydrators are worth a bleep and can have huge variances.
I totally agree with this, and that is why I also use a digital thermometer with mine so I can accurately set and monitor the temperature. Usually run it at 130-132 and have never had any problems.
Depending on the brand of the ball, 130 - 132 degrees voids the warranty.
Motiv, Radical, DV8 and Brunswick all state in their warranty that a ball is void of warranty if it is exposed to temperatures above 125 degrees.
Make sure you know what your device operating temperature is and what the manufacturer recommends.