[mngundog]

I am currently working on some ideas for a cheaper one. Here is one from gondogsupply, however they are still pricey also!

http://www.gundogsupply.com/retired-gunners.html

Same concept, would just need to modify it a bit.
http://www.gundogsonline.com/bird-launcher/innotek-bird-launchers/innotek-auto-backer-rb-100.html