A cheaper alternative to the $4500 folding kayak would be the Sonnet 16. Designed by Tom Yost. He has designed some beautiful kayaks. From aluminium frame foldables to wood frame kayaks to inflatables.
Since I am without any proper metal working or wood working skills. I am focusing on the inflatable. Kinda hard to ask those workers in the metal shop to do it for you too, because they only know how to do hands on. They are not thinkers.
Here are some pics:
Many other kayak designs are available Tom Yost's Website