I suspect that most of the real Panzers and Tigers ended up in pretty sad shape by the end of the war. Probably pretty hard to get hold of them.
True. But one thing about these panzer III/IV and Tigers is that it would seem to be simple to model/replicate them due to all the right angles. While I would never want to be in one while in battle, I love the way Panzer IVs look! I bet if those two movies in question (Patton and Bulge) were made with todays technology, they could shoot scenes with some of todays repliacted or surviving panzers (and Shermans) in action and replicate them digitally for large battle scenes.
I recalled some authentic tank scenes in Band of Brothers and did a quick google on that subject. They did not have large tank battles to deal with, but they did recreate a cool replica Tiger and StugIII as explained here:
BandOfBrother Replica Ger Tanks
Theres a bunch of static Panzers and Tigers in museums and a few actually running: