That appears to be a Edelbrock Elite series limited run air cleaner.
Your basicly SOL on it. Good luck in your hunt.
All the parts for it are still available except the base. So maybe a custom made bottom can be done?
Some fellas here have a similar air cleaner dubbed "Mr. Norms" 6pack air cleaner for sale in that forum.
http://promaxcarbs.bizland.com/id1.html
Or you could check out Edelbrock 4239 air cleaner, I believe Summit has them.
They aren't identical to that one but similar.
You need to find and borrow a base plate to copy a d create your own custom unit.
I have looked at the Mr. Norms for sale here and they aint cheap. Lol. Hoping to find something a little easirer to find a filter for.
Fram still sells the filter for Mr. Norms air cleaners.
I have a Mr. Norms hanging on the garage wall for 20 years now.