Before you send the extra money, you might want to go to
www.kslegislature.org and look up this statute, 50-626, Unfair Trade and Consumer Protection Practices. If the situation is as you describe your stock-maker has a problem.
Under Kansas Statute 50-631, the Attorney General is empowered to investigate claims under 50-626. Their Hot-line number is 800-432-2310, as you are not in Kansas; you may have to dial the toll number785-296-3751.
His collection threat is contrary to Kansas law, there is a very specific method of securing what would be a mechanics lien on personal property and what you are describing is contrary to Kansas statute, I think it is under Chapter 58 of the statutes.
If you contact the AG office you will find them most accommodating, I am not an attorney and I am not giving you legal advice, but as I do a lot of work for car dealers, and I have to respond to several AC investigations a year and they are through.
Even if you do send the money, once you get the stock, I would still file a complaint, as the AG can impose fines penalties and award compensation
Good Luck
jon