What I'd like to see is an oval air filter modified to clamp onto the carbs. I know I have seen one that would be about right, expanded metal screen and all. I'd even be willing to sacrifice the fake oil tank for that.
Anybody have measurements handy for the carb spacing and diameter? I think I may have found just such a thing here.
http://www.martelbrothers.com/pages.php?pageid=25