It sounds like you want something packable though (rather than a full sized 30" type bow saw - one of the more effective types.)
Believe it or not - I just discovered this- the #8400 Folding saw from Coughlan's actually cuts bone quite well. It has one of those wood cutting blades, a Japanese type wood cutting tooth I think, which isn't very sharp to bump against. I have known they cut wood like crazy but I also discovered that they work very well on bone. I used one to make quick work of the brisket on a recent moose (after first cutting through several dozen 3-4" alders along a path to the animal.) I also cut the spine in several places. Finally, I used the same blade to very cleanly remove the antlers and skull plate from the animal. It cuts solid bone very well, if a bit of patience is required. You could easily remove the brisket from any of the smaller deer in under two minutes and a pelvis wouldn't likely take much longer. I have noticed that the teeth on this type of blade don't work well when clogged with tissue or hide when sawing heavy bone - ribs okay, but not scalp- consequently, it works better to cut soft tissue away first.
http://www.coghlans.com/catalogue/productList.php?catID=23It's worth a look and the price is right on these. Real handy for cutting trails, etc. too, if needed.