David,
I have the same linisher, and have got 915 x 100 belts from Axminster, and cut them in half. It is a simple task to divide the width into two by cutting on the inside using a "Stanley" knife or similar. I made a simple jig to act as a guide. Even if not very neatly cut, they still work. I have found that if heavily scored, the belt wil break apart, but that may depend on the grade of belt. Whether the Axminster belts are strictly "metal cutting" I don't know, but I have found them satisfactory. There may well be other suppliers.
Regards
John