There"s actually a good number of places that will give any Vet a discount. At least locally Lowes and O"rileys auto parts do. Quite honestly, I think locally some of the Home Depots will too, but I the way I understand it, it rally just depends on the managers/clerk of the individual store.
And after googling for a list of all the places for my Dad, I"ve come to the conclusion just ask very politely at any major store, "Is there a discount for Vets?" And the two worst answers you can hear are No, or I don"t know. If the former, just say thank you and continue to pay. If the latter, you can do the same, or try your luck to see if they can find someone that knows.