BlackIce Extreme, or if you really are on a tight budget, a simple BlackIce.. Short of that, you're going to have to find a way to fit the standard 6x7" heatercore in.
There is one possibility.. That Geo heatercore from a junkyard.. If you can find a junkyard with that model of Geo in it, you could probably get it off them for $10 or less. Pump some CLR though it for a day or two and it should be good to go.
