Do you want long or wide? You can get either but you'll need different designs if you want cheap. The normal process lenses I think you'll need to get the 360mm to cover the 8x10 well. OTOH the wide process lenses can cover 8x10 with a 210mm.
These supposedly cover 8x10 and if you're lucky will actually screw into a shutter. OTOH the sellers never seem to ship to Canada so I haven't been able to check.
Do some search on googles newsgroup archives for info.