Outer air filter for MF 231S

[def38]

I am attempting to replace the outer air filter on my 231S. The current outer filter has a dished steel plate with a captive wing nut that secures the filter in the housing and locates the filter over the inner filter. I ordered a WIX 46319 filter but the filter, while the correct dimension, did not have the steel end cap and wing nut. Instead, the WIX filter had a rubber flange incorporated into the end with the correct soft rubber sealing ring at the opposite end. Does anyone know of the correct aftermarket outer filter for the 231S?

Thanks in advance.