Anyone know of a vendor which makes a 12-port 1000BASE-LX Switch?

The LX-version of the Extreme Summit5i is close (12 LX + 4 GBIC):

Regards,

Marco.

Or for a LOT less money you can get a netgear gsm7312, which has 12 sfp modules. Get 12 lx sfp modules, and it still works out cheaper.

However if you need stable layer 3 switching, go with extreme. If ya just need layer 2 stuff, the netgear ain't a bad choice.