Napa has a "Heater Hose Removal Tool" #730-5632 for about $5. It is basically a 2-piece plastic collar that you assemble around the heater core pipe and slide into the fitting.
I tried to replace both fittings once. One of the replacements just wouldn't go on. After bruising my ribs, I finally just gave up and used one old and one new one. A dealership probably has replacements--expensive, but maybe they'll actually work. The cheap ones I tried go use were Dormans from Rockauto, part #800-409. I had a new custom heater-hose assembly, so Chris's idea about clamping the hose on with no fitting wouldn't work.
I should say this was on a 2001.
Good Luck