You can't farm it out somewhere?
If it's only a 12 week job, I'd think it would be much cheaper to have a service do it. Of course, if there are security issues involved, etc., well...
Some other possible vendors to check out:
[link|http://www.suspensionfeeder.com/|http://www.suspensionfeeder.com/]
[link|http://www.streamfeeder.com/|http://www.streamfeeder.com/]
[link|http://www.intelligentline.com/products.html|http://www.intellige...com/products.html]
I found these looking for "envelope feeder". Thomasnet.com has some more industrial links that may be useful.
HTH a bit.
Cheers,
Scott.