How about a slinger followed by a felt seal? The slinger can be made
from an o-ring. Felt will catch any tramp oil, is cheap, & can run dry.

The felt will wear. It's used in many older aircraft wheel
bearings (even some newer ones, and it doesn't work that well. It has
to be saturated with grease to prevent water uptake, and thereby
attracts dust. If it soaked up oil it would become saturated and allow
the oil past.
Autos and trucks abandoned felt seals in the '40s and '50s.

Dan