@ Marc Shea, The old Sherpa Raft design would likely be relatively inexpensive and was exactly the boat these posters are looking for. Not a white-water boat (no spray deck) but 10 inch tubes in a donut construction, meaning a top and a bottom, like the Feathercraft. It was symmetric and had an upturned bow and stern. The tubes can be no smaller than 10 inches and the boater needs a good, stiff paddle to backpaddle.
Throughout the 1980 and 90s many, many Alaskans paddled Class II in vinyl pool toys they bought at the equivalent of K-Mart. They were cheap, lasted one or two trips and were a chore to deflate with their tiny valves. I knew guys who walked the length of the Alaska Raneg in 1996 and they deflated theirs by stabbing them with knives! Then they'd put a piece of duct tape on the hole next time they needed them. Bummer is you can't tie the pack in well, but not too important in Class II. The Sevylor Trail boat was the worst as it was far too small with a little 5" bow tube -- it was a freakin wave shovel!
Believe it or not, in Class II it's not the boat it's the paddle that makes the difference -- that and the paddler! The paddler's got to backpaddle and ferry to keep water out of the boat and put them where they need to be and a vinyl raft and a good paddle is fien for that.
We used to have these same conversations in the 1980s about Sherpa packarafts that cost $500, a lot of money for 20-somethings like us who worked less than we adventured. We paddled the vidnyl boats and trashed them on single trips and so went ahead and as Vacco suggests invested in the real thing.
An Alpacka Scout or an NRS at $500 is the Class II ticket right now -- but that's a lot if you never tried packrafting before, so go to Wallmart or wherever and get a vinyl boat and try out packrafting with a rented sea or whitewater kayak paddle (one piece carried in your hand).
And buy my book!