No. No one makes tape for that. 300psi is more than most tapes deal with. With only a couple of pounds of refrigerant to begin with the system begins to suffer when only one half pound leaks out, tape wouldn't buy you enough time to make it worth while if the leak is big enough to be a problem now.

Besides, if you've got an A/C line running to the radiator, you've got bigger problems. The radiator is for coolant, not refrigerant.

MV