You can probably find an auto glass company that will order or cut the glass for you.
I have resealed the rear glass in an 05 vert. I used the Black Permatex (comes in what looks like a cheese wiz can). Stayed sealed for the two years that I owned it through a couple reasonably harsh winters.
You can probably do something similar or see if the auto glass place will install it (no idea).
Either way though, it should not be necessary to replace the entire top if it's in good shape.