$42!!!! Ouch, just checked their website and that is indeed the price. Shows what happens when beancounters buy up companies and start selling to kids with disposable income (present company excepted, of course). Grumble.
The basic Go-Slo is a simple 555 timer chip that "stretches" out the control pulses to the servo. Here is an RC Groups thread on that, the Brent Dane circuit is simple and easy to build. Let me dig around and see what else is available.