the Niobrara in northwestern Nebraska would be an interesting contrast to the Current. There's an upper section below Valentine which runs partly through a wilderness area, and then a lower section that is well-served by outfitters, campgrounds, showers, and has some spunky class 2 rapids at decent intervals. The Niobrara runs west to east, and so you'd be assisted by prevailing winds.
The Upper Cedar River in NE Iowa can make a good multi-day trip. I don't know about camping, however.
Someone mentioned the Red River in KY. The upper Red is kinda class 3 and seldom has enough water. The Lower Red is usually runnable through late spring, but no showers that I know of, and maybe not as long as you want.
The Green River in KY is long enough, has enough water at most times of the year, and ends opposite Mammoth Cave National Park.
On the showers, maybe you could get some of those solar heated shower bags. Hate to see anyone limited by availability of public showers.
Cartop Kayak Carriers
PFD's (Life Jackets)
Free Standing Boat Racks
Touring Kayak Paddles
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