No I think your best bet is a funeral home or hospital morgue. They deal with dead bodies its their job. Army is for training soldiers.
Creepy thing to put in forums Um yeah I'd go with funeral homes or your local hospital perhaps? Worth an ask. If not, you could always use like a clothes hanger cover...just sew the bottom end...hey presto you have yourself a body bag.
My suggestion is along the lines of the others, u should first google it in ur area, it is possible that medical supply places might have it, u should also check ebay, do ask local funeral homes,if they wont give u one then ask if theres anywhere u can get one, id also suggest a halloween supply store or a halloween supply site, and if u dont get anything there u could get very creative nd get two suit covers (u know the ones whn u buy a suit andthey put them over it so u wont get it dirty) and sew the ends together
But seriously...you cannot buy one from a real vendor as they are not exactly used much by the general public. They only kind you might be able to find would be an old used one......and I don't know about you, but that seems a bit creepy knowing a dead body might have been in your science project.
I don't believe that they are avail to the public. A military ruck sack should do the trick though. They're about 4 feet long - at least the one I have is. And you can sow the top closed and put a zipper down the side. Another option is taking a twin sheet, folding it in half, rolling the top and bottom - sow it, then sow a zipper in where there's an opening and tada! Body bag for 15$. I also recommend asking your teacher if putting perishable food items in your project is allowed - I'm sure you understand that 99% of teachers bring the projects home with them to grade and the rare 1% that don't leave it at the school - so you may want to check with the principle as well. This is not a project about decay right? Because with all that perishable meat it will be in about 12 hours after staying in room temp - especially in a school. I wish you all the best on your project! Do give us an update - I am curious as to how all this will turn out!
I suggest you try using a suit carrier. They sell leather ones. You could use a decal or whatever to make it fit the specific look, but that is something easily accessible and similar looking.