There are 2 sizes. If you're making the cabinet, the ones makitmama posted might be OK, but there's another option too. The 99s and other 3/4 size machines "typically" use a different hinge type.
These ones:
http://www.ebay.com/itm/Singer-Sewin...item460b0d455c
On second thought, there's a chance they're interchangeable if you're making the cabinet. I think my 15-90 has those too, and it's a full size machine.