Our grocery store sells them too. Used to drive me right up the wall when I was still working! The only time I could get to the post office when they were open was on Saturday mornings. I tried to keep up with stamps but was always running out, but there were vending machines for stamps in the PO lobby that I could use. Then I went in there one day to buy a stamp for something that I HAD to mail and the machines were GONE! And those people had the nerve to put up signs where the machines used to be that read, "For your convenience the stamp machines have been removed from our lobby"!!!! WTH???? That's when I discovered that they had them at the grocery store!