Find one from a Mercruiser 165 HP inline 6 engine. It's just a 250 straight six. The cover is made of cast aluminum (just like the Clifford and Offy) and can be gotten off Ebay pretty cheap. I've seen them for 15-20 bucks (which is a heck of a lot cheaper than the 100 & up you'll pay for an Offenhauser). They are taller than the stock cover and will probably work for your application.
If your timing is right you can grab one of these cheap. Beware though - "mr.hotrod6" is snagging 'em, cleaning 'em, and getting $70 & up for them.
-magic mike-
