Does anyone know of web-based cross-reference charts for common service parts (oil and air filters, spark plugs, etc.)?

I've got a dual-plugged R75/5 and am trying to determine alternates to the NipponDenso X20FS-U 1/2" plug used on the bottom ports. The only site I've found with cross-references is Champion's, and it didn't recognize the ND part number. ND's site didn't help, nor did AutoZone's.

I'm also looking for the correct K&N air filter and alternate oil filters (like Purolator's PM 2099).