My roommate has a 3d printer and she printed a few pairs of cat ears for her work helmet.

34 bucks for some fabric and Velcro. For probably $20 I could make multiple pairs of them.

At my old unit, we somehow managed to justify (and purchased) a really nice 3D printer for my shop. One of the pilots came in at one point and printed a 9 inch long purple spiraled Unicorn horn with NVG mount locking points built into the base, and attached it to the flight helmet of another pilot who everyone thought was a bronie. It was a masterpiece and fit perfectly.

Far more fierce than the Pickelhaube.

Also, holy shit, have you seen the skirt and thigh-highs on the Prussian infantry that wore Pickelhauben? That would go perfectly with cat ears!