"...Not sure about orange 55 liters availability though..."

If you befriend someone at CalTrans, or just go to them and tell them what you are doing, they might give you a bunch of their nice bright orange 55gal bags. Or you could adopt a highway and just "borrow" some. Of course those suckers are about ten mil thick, that makes them a little hard to squeeze into a small sized kit (this I know from experience). But being so thick, they really work for emergency shelters, etc...