For future reference, says on the item specification - "for models with ac". 
Can get one from there or your local motor factors.
EDIT: You guys know there's a locking-off hole on the tensioner right? Don't have to tie it to anything lol, just stick an allen key in the locking hole when the tensioner's pulled back. Helps if you tape it to a long screwdriver or something for better access.
Dec, even for someone neverseenspannersbefore-new to mechanics it won't take more than a couple of hours to do.
Can get one from there or your local motor factors.
EDIT: You guys know there's a locking-off hole on the tensioner right? Don't have to tie it to anything lol, just stick an allen key in the locking hole when the tensioner's pulled back. Helps if you tape it to a long screwdriver or something for better access.
Dec, even for someone neverseenspannersbefore-new to mechanics it won't take more than a couple of hours to do.