727 inspection cover

Hey everyone,
Please see attached pic. My car we just put the 727 and 360 (both rebuilt) in is missing the inspection cover. I have no idea how that happened. I can't even recall if that transmission had the inspection cover to begin with. It is what it is.

Moving forward I would like some info on this:
-Are there different types of covers? If so which one(s) will fit mine?
-Are these a rare high dollar item or something? Or cheap dime a dozen?
-Any recommendations on where to find these or what exactly to search for, so I can locate one that fits my 727?

Thanks!!!