I made one from a stip of aluminium about 1" wide, then drilled two holes to allow a nut and bolt to go through, the end of bolt needs to be about 20 mm long max, the bolts go on the lug on the casting and in one of the slots in the casting
Works a treat.
There is a 4mm hole so you tension the spring until a 4mm pin can be slid in place, this keeps the tensioner in the locked position
Cheers