Heater core recomendations

I have been trying to find a replacement heater core for my wifes' 2003 Chrysler Voyager. The dealer wants $230 for the item. I have found 2 places that I can order for half that. What I was wondering is why do the major auto parts stores only carry the rear core and not the front if they carry any at all.

Stay away from the ones from the auto parts stores,they do not fit right at all.The one from the dealer fits in better.My father went through this,got one from Carquest and did not fit and the one from the dealer was the better one.