1999 Other Jeep Models My radiater is cracked

I am sure of this as my mechanic checked it out. We are going to trade this jeep into the dealership for a new car (we've had it with this jeep!). Is there a "quick fix" type of sealant that would work so we can actually drive the car about 20 minutes to the dealership (rather than pay the $500 repair for a new radiator- even our mechanic thinks we shouldn't do that). The car is valued at only $2000 or so. So putting $500 in would not be good.

Our mechanic said we would probably have to stop about 1/2 way to put water in it (when the engine cooled back off). Just wanted to check and see if there were any other ideas? I had heard from someone there is a "sealant" you can buy for the cracked radiator for a quick and temporay fix.

Thanks!