well.......bandsaws take a range of blade widths. Usual procedure in this situation would be to google the make and model to find the specs. Failing that (if you have no access to a computer for example) find a Clarke dealership and telephone them to find out.
I might be out of line here but you might get a better response with the addition of the word "please"
You are probably going to struggle to get one unless you can get an actual spare part from machine mart. You could make a simple one fixed at 90 degrees easily enough. I wouldn't spend a fortune- they are not machines for cutting a mitre straight from the saw so you may find it isn't that useful to have a super accurate version.