Thanks guys... I appreciate the suggestions. Will definitely look into this.
Since I'm pressed for time (need the car by Monday), I went with just a regular hardware store type o-ring for the time being. Not sure if it is petroleum friendly but it should hold me over until I get one that definitely is. Switching it out shouldn't take more than an hour.
Just for the record, it appears the o-ring size appears to be 7/16" ID, 9/16" OD and 1/16" thickness.
By the way, car runs great with the new speed sensors - knock on wood.