The SD2 runs on 12v and heat cartridges can range from 20-40 watts. Any of them will work as long as they fit dimensionally. So you can measure the diameter and find one that'll fit. A word of caution though, the stock hot ends on a Solidoodle aren't exactly known for being the best. There's a good chance you'll fix the heater, only to find out the nozzle is clogged. If you are serious about 3D printing, the best advice I can offer is to buy an E3d hot end. The Lite6 is far superior to stock. There's also the full blown V6 all metal hot end that will allow printing of exotic materials like nylon.
Everything you'd need to get up and running can be found here
http://www.printitindustries.com/
Printit Industries Model 8.10 fully enclosed CoreXY, Chamber heat
3-SD3's & a Workbench all fully enclosed, RH-Slic3r Win7pro, E3D V6, Volcano & Cyclops Hot End
SSR/500W AC Heated Glass Bed, Linear bearings on SS rods. Direct Drive Y-axis, BulldogXL
Thanks to all for your contributions