Dana Design internal or external depending on preference would fit the bill. They can be had on eBay for south of $200.
This^^ Specifically, an old DD Terraplane which is what I used on my first solo BP hunt. I think I paid $110 or so on ebay.
Another option is the LLBean carry-all pack, used with drybags.
http://www.llbean.com/llb/shop/6439...;attrValue_0=Olive&productId=1077114I bought this a few years ago, later buying Kevin's Paradox pack from SeekOutside. I still have the LL Bean carry-all pack and just can't let it go. For the money it is a great pack IMO and very versatile. I can strap on a tree stand or a 50 pound bag of fertilizer(for what reason I don't know) but gear can be loaded in dry bags and meat packed out. Very comfortable to carry.