Thomastik spirocores are very easy to find--most local violin shops will probably have some around. They come in four sizes
Solo (designed for solo tuning)
Weich (the thinnest and lowest tension for regular tuning)
Mittel (medium--these are really common and widely used for jazz)
Stark (highest tension)
They're very lively, zingy strings, but they aren't easy to get a sweet tone from starting out--they tend to sound a little raw. I'm not great master with the bow, and it took me a while to "tame" them. I'm using the weichs.
You can also get them online from some talkbass sponsors--uptonbass,
www.gollihur.com, lemur music, etc. Here's a link to adealer who's local to me:
http://www.bobshouseofbasses.com/sea...mastik+Strings
You might want to spend some time looking through the reviews here--there are many better players than me who post regualry about strings