I got mine some time back by placing a WTB for $40 (Not in the best of condition, but hey, NSC checked it out and it's in perfect working condition and it's a plastic case for batteries :bsmilie: ) in the B&S sub-forum. The cable replacement is ard $65 IIRC.
Or you can PM sykestang to see if he has or can get a new SD-8A for you. I know he has one for sale some time back. Should he been sold by now.
This was the estimate for my unit :
2nd hand SD-8 : ~$40 (Depending on condition)
Cable replacement : ~$65
Total : ~$105