I've just recently replaced the throttle cable (quadrant to throttle body) on my '97 Spider. I obtained the cable from Mangoletsi, Knutsford. Tel: 01565 622899. They'll want your VIN/Chassis No to check the part number. In my case, the part number was 6062 8939. Including postage it was just under £30.
Getting to the quadrant was a pig of a job! It involved removing the plastic undertray below the engine; removing the front section of the exhaust. From underneath the car (and viewed from behind the gearbox), removing two 13 (or 14) mm bolts at the ends of the inlet manifold): removing two 15 mm bolts which secure the inlet box to the engine mounting bracket. None of these bolts were rusted but required a torque wrench to get sufficient leverage to slacked them. In my case the engine mounting bracket had an additional metal lug on it which served no purpose other than to prevent me getting a socket and extension bar to one of the 15mm bolts. I used a Dremel cutting disc to cut it off. From above the engine (after disconnecting the battery), it's just a case of disconnecting the throttle body, wires and hoses etc before easing the inlet box out to expose the cable quadrant box. Re-assembly was aided by smearing some washing up liquid on the inside of the rubber inlet 'hoses'.
I used four concrete breeze blocks under the wheels of the car to get all four wheels off the ground by about 6 inches.
I hope the above is of use to someone out there.