Well, after posting my previous message my Mom called me (she shops at the same places I do) all excited b/c she found the Fels Naptha – at Randalls!!! Apparently they were just out of stock the time I was there. She said it was on the bottom shelf in the laundry aisle. Maybe your local Randalls has it too.
(Ours had the washing soda on the TOP shelf of the laundry asile!)