I made mine out of steel. Buy a uni or whatever filter and get a 1/2" of tube milled to fit the inside nice...make sure a couple of tiny grooves around the cyl. to help the filter clamp on better.
I migged it onto a light gauge back I traced with the sponge piece that came with uni .To seal it up to the air box, I used 3 little bolts to fasten plate to airbox( critical hole placement nec. be careful)! I used silicone in final assembly too...
Be sure to plug small hole in back of filter if it is designed for stock warr.
You might have to trim off the stock tabs in airbox for fit.
Works good and cost nothing but time. An afternoon of fun. I had a couple beers at my buddys shop waiting for machined tube, and fixed up my ride before dark.
I have 3 months on it and love the confidence of more air and less worry about the crappy original filter. Works awsome.