Umav S-12 Vista Scanner

I'm looking to purchase a Transparency adapter for my Umax Vista S-12. I need to scan a large amount of Transparencies ranging from 35mm, 4x5, 5x7 and 8x10. Since the scanner is in fabulous condition because I haven't used it much, I would rather find a Transparency adapter for it then purchase another scanner. I have an older Mac which is SCSI campatible and will only be used for the scanner. Can anyone give me a lead to somewhere I could find an adapter.
Thanks