I paid about £25 for the one I've got tucked away in the garage. I wouldn't advise paying much more than that. Could of got one which was identical to the Ruston's seat, but that had cracked severely. I'd have a look round the stalls. There is usually a stall with one or two implement seats on. They aren't the comfiest of things though Nick. Doesn't your cousin have one for the Garrett you could make use of? He won't need it in a hurry!
And leave the one alone thats near you!
