The "key" component of any extension rails are the gear tracks. If you can get rails of any kind with compatible brass gear tracks, you can have a woodworker craftsperson make an extension rail to fit your camera. You can also have an existing extension rail reworked to "fit" as long as the gear tracks are correct pitch. The hinge and/or attachment wing-nut can be replaced or repositioned.
On my Agfa/Ansco triple-extension 8x10 the front rail attachment is rather small, and normally not needed, except for very long lenses. The Agfa/Ansco design more or less had telescoping rails built in, unlike a design such as the Eastman 2d, which did not.