I had a good number of mitre joints to cut on my bandsaw for some framing I was making. So a little time at the table saw with some careful cutting checking and I have a nice little mitre joint insert for the band saw.
This isn't a new idea, but here is my simple implementation. 2 layers of 18mm plywood glued together with some high density plastic (from a cheap chopping board) the correct width for the slot in the bandsaw top screwed onto the plywood. This stops the wedge from sliding out.