If you like K&N products, and want a rear filter that you can wash & reuse... then have I got a tip for you.

K&N does not "officially" make filters for the FEH.
However, they do have equivalents that do fit.

For the rear battery compartment, order Part Number YA-1602-U.

This is really an engine intake filter for a Yamaha Motorcycle.

It is however, close to the same size as the battery air filter, ( a bit larger but the rubber border is easily trimmed with a knife ) and about 10x more durable.

Cost is $40 ( free shipping ) and it will out-last the vehicle.
If you want this to be the last filter you will ever buy, then go for it.

-John