There is nothing special about fitting an air filter on these engines. Just measure the existing air intake hose OD and find any suitably sized canister-type filter. K&N are expensive, but work well. I use inexpensive Purolator ones on ours (and don't remember the actual part number - I just go to the autopart store and open boxes until I find the right size).
You will not find anyone who can cross-match because there is nothing to cross-match to. The original part is not an air filter - just a piece of cheap
foam stretched on a wireframe.