cm870 belt tensioner

[Chamberpains]

I also shop ebay for belts. There are a lot of businesses getting rid of old stock cheap. I picked up original Continental part # belt and a gatorback goodyear belt for $30 free shipping just last month. I also had to find a belt that was 2" shorter because my alternator pulley was size reduced somewhere in its molested life.
With continental part #'s, the first #'s are the # of grooves and ridges across the belt that needs to match your pulley and the 2nd set of #'s is the total length of the belt in millimetres. So if you need a shorter belt just knock off 25 millimeters per inch and search that part number. Although most belt #'s end in 0 so just round off in the safe direction and you should find the length your looking for.