It is protecting the swingarm whilst not wrecking the chain - so if you cannot repair the old one fixing some 'sacrificial' ally to the swingarm would do for a short while - clean it all well and stick a couple of layers of 1/8th or so plate around the swinger - in the same place as the guard - with some decent double sided tape, and keep an eye on it - should be OK for the short while. The plastic original guards wear down until the chain rollers bear on them rather than the side plates - thus they wear slower, so the chain plates will eat into the sacrificial plate but should (repeat should) not go deeper than the difference between the side plates and the rollers, so if the added plated ar somewhat thicker than this the swinger should be OK till the real bit arrives. If you have a nice thick chunk of nylon or similar you could warm this and bend it round (have used nylon bobbins in the past) etc.
R
