I have an ST-4 in excellent condition. It's about 3.5 years old and in perfect working condition. In fact, I just used it a few weeks ago to guide the image of M27 below taken with my HX-916.
Includes extra long 40' serial cable and parfocal eyepiece (I never had to focus beyond using the eyepiece).
$600 + shipping
Paypal accepted (although +2.9% for credit card transfers)