well for a pred 1 style suit there are some fish skulls, on the tight side there appears to be a gar skull ( oblong head, long slender mouth ) well I know this may sound gross but why not take the skulls of dead animals (completly decayed , nothing but bones left) from local parks, I know I find them all the time, the only other alternative I know is to go to a taxidermist and see if he/she has any lying around,
-Mike