Patrick: I buy my GL-4 from Napa or Amazon. If I need it now, I get it from Napa. If I can wait a couple of days, I get it from Amazon. It's the Sta-Lube brand, and I get it in the gallon size.
That stuff is jacking up in price. I bought some back in July and it was about $26 for the gallon.I found this last night. NAPA closed all of there local stores here. We used to have a hub less than a mile from my house too.
https://www.amazon.com/gp/aw/d/B000M8RYMC/ref=mp_s_a_1_1?ie=UTF8&qid=1505044957&sr=8-1&pi=AC_SX236_SY340_QL65&keywords=gl-4+gear+oil&dpPl=1&dpID=41yKSMlBnuL&ref=plSrch