I have experimented with a few different elements for these filters when I do dual carb. intake conversions.

The original filter media appears to be nothing more than aluminum shavings.

Have had the best luck replacing the old media with the copper material found in scrub pads.

I have located a few different paper lawn mower filters that will fit, but as already mentioned.... they do restrict air flow.

Attachments
air filter.jpg (134.12 KB, 352 downloads)
intake.jpg (100.55 KB, 345 downloads)