15-03-16, 11:49 AM
I think it's fairly common for them to crack where it attaches to the frame (where the bolt goes through). If you don't find a second hand one, you can give plastic welding a try - Delboy's garage has a decent video ( https://www.youtube.com/watch?v=k7GRNvPSf7k ). It will take a little effort to make it look perfect, but if you aren't too bothered by the finish it's easy - you just need a soldering iron.
I bought a spare "good condition" infill off ebay, which turned out to be cracked in the same place as my original, so I gave the plastic welding a go last week (will try to post a picture below. It needs grinding down and finishing now.