lost a magnetic piece

I lost a piece from one of those "checkbook" chess sets and just wondering if anyone knows where to purchase some

Check out chessmate.com http://www.chessmate.com/chessmate1.html

If you scroll near the bottom of that page you'll find kits of those type pieces. I don't know if they'll sell individual pieces but it couldn't hurt to ask.

I don't have any of their products but they look like some of the nicer travel sets I've seen.

If you have any problems purchasing one piece then you could order a strong disc magnet at Amazon or Ebay and simply glue the piece image onto the magnet.  You should be able to get approximately the same size magnet as the piece you lost.

http://www.ebay.com/sch/i.html?_nkw=disc+magnets

just use chewing gum and stick it on there dude