Advance Auto parts sells a small breather filter for $10. They also sell a y vacuum fitting. It's like 3/8 end to end and the y is like 5/16. The rubber hole on the breather filter is on the big size but a small piece of the factory hose jams in nicely and since it came out of the valve cover it fits perfectly. The gas vent plugged in the 5/16 on the y fitting. I can take a pic of my description is bad. Btw they have, red, blue, and black filters.
It's the cleanest thing I could come up with. I've seen several people put a small lawnmower inline filter in the end of the gas vent hose and tuck it under the seat. Seen long hoses run down under the frame into the atmosphere. No filter. Seen catch cans on several.