I bought the generic 4" chrome breathers off of a vendor at a swap meet, threw away the top used the bottom and put some yamaha 750 oil filter covers on for tops. Thier the perfect size. I'll see if I've got pics and post.
There's a flathead engine builder in SoCal, name escapes me at the moment, that makes 97 and 94 aircleaners from pistons- super cool looking, but pricey. They don't look like they would be that difficult to fab for tops, tho.
I run 2 finned stacks from Maund. www.maundspeed.com I get alot of compliments on these. Another person is Charlie Price? I think that is his name. www.vintagespeed.com He has two styles of frogmouth scoops from Australia. I really like these. Just my input.
Heres some velocity stacks made from exhaust pipes on my old 26 and the other helmet aircleaners are brand new from vintage speed. The carbs are brand new rochesters but the same type of cleaners can be bought or made for 94s and strombergs
Here's my attempt at "cool" air cleaners for my Nailhead although they would only screen out birds and large rocks. It was my way of getting the Tommy Ivo roadster look without using an actual Hilborn setup. Installed it on my '32 for a few car shows to complete indifference so have gone back to the good old reliable Edelbrock Performa rather then h***le with a bunch of leaky '97's. Plus my favorite from the LA Roadster show a few years ago.