I think this is the one you are thinking about
The guy who updates the Walmart files is very active at keeping up. I corresponded with him a few times to obtain some more data that wasn't in the files on the above website. I like to format my GPS files differently than the files on this website, and he told me where he posts the extended data. It just isn't in a GPS friendly format.
I had my own way to creating GPS files for a Garmin for the Costco locations that had gas stations. But Costco took the link I had been using off of their website. So I can't update my file.