Celtic 983, I hope you check back, it took me a while to find the address where you (or anybody else) can probably still get Celtic Stone casettes.
House Morningstar
P.O.Box 20094
Houston Texas, 77231
http://www.housemorningstar.com
info@housemorningstar.com

They have a store in Houston at 11246 S Post Oak Road #217, Houston, but I saw on one site I found on the Google search to call for an appointment, so I'd keep that in mind. I didn't see any Celtic Stone casettes on their website, but I'd ask just the same. They have a neat variety of things; their main interests deal with horses and things medieval, but there's such a variety that I frequently buy Christmas gifts for people who aren't interested in either of these subjects. And they're nice folks.
Celtic Stone is still one of my favorite groups to listen to; my kids keep stealing the casettes to listen to them as well. I thought they specialized in novelty songs when I saw the titles: "Who put the Jalapenos in Mrs. Murphy's Chowder?", etc., but it turned out they just had an inspired ear for tune juxtaposition (in that case, the Irish Washerwoman and The Mexican Hat Dance) and the musicianship to pull it off. Great stuff!