I've seen them at Arizona Charlies (classic) in Las Vegas. Also at Venetian. I don't think they are issued by the hotels, though. They probably give permission to use their name and sell them in the gift shops. Generally, the commemorative phone cards are terrible deals if you want to use the calling time. As Marv pointed out, the issuers sometimes go out of business and start up under a new name to eliminate the liability of all the cards they sold. No 60 day notice period on calling cards [g]!

By the way, there's a category on eBay that includes phone cards, as well as the slot club cards that many of us collect. It's not under the casino heading.