It is getting cold and I have no heat!!!

OK... here is the problem... The heater core leaks.... lol.... I can not find a replacement core... I have the box set up in the floor in my '62... I had another box and tore it apart and someone soldered it up around the temp control and took the temp control out???? I assume it was leaking around it??? Don't know??? I brought the auto parts stores transpro radiator/heater core/AC condenser book home and can not find anything that even resembles what I need.. (one with the temp control) I guess the question is.................
What is everyone using for a heater core in the little box heater that is mounted to the floor in our Econolines????????? Do you think that a radiator shop can find the leak/leaks in my unit and fix them???? any suggestions or stories on what you have done for your heat is greatly appreciated.... Thanks guys............

Your cores were talked about awhile back in "between the seats 'e' " type in heater core in the search block and the posts will come up. Good luck.