I have a 3170. I don't use it anymore, but still, I don't want to part with just the masks. They'll go with the scanner if/when I decide to sell it.
I can provide you with measurements, however. It shouldn't be difficult to cobble up a slide mask, since the slides just rest on the glass. The ones for 35mm negatives and 120 will be more difficult, though. If I were you, I'd keep my eyes peeled on eBay for them to show up.