My brother has come up with what I believe is a very good invention
and he has asked me to be in a partnership with him to develop and
market his product. He has already created a crude prototype that
proves out the concept.  For obvious reasons I do not want to be too
specific, but his invention could be described as an innovative
plastic container suitable for food products. To see if it would be
feasible to develop his product I would like to get the names and
contact information for a number of plastics fabricators who could
produce a more refined and well designed prototype. Hopefully, the
company that produces a good prototype could later manufacture the
product for us in large quantities.
    Secondly, because it might be prohibitively expensive to pay for
the development of a prototype, I would like the names and contact
information for several companies which do product development
partnerships with the inventors, that is partnerships where the
inventor provides the invention (but no money) and the company
provides the capital to develop the invention, and where the profits
are equitably shared between the partners according to some pre-agreed
formula.

As for manufactureres the list would be too long to type do a Google
search for Plastic Manufacturer and you'll get  a ton of links

://www.google.com/search?hl=en&q=plastic+manufacturer&btnG=Google+Search

To find a company that will manufacture the product is a different
story altogether, you'll need to deal with them one at a time
yourself. Lastly "and where the profits are equitably shared between
the partners " ahh sorry to have to break it to you but there is no
such thing. The standard agreement is you provide the invention they
manufacture and sell the product you will get royalties of between
.05% and 3% of the profits, often they make thos profits on an after
tax basis reducing your potential income even further.

Before you do any of that you should procure a patent for the product,
that will cost you around $ 4,500 if you do it with a lawyer or about
$ 600 if you do it yourself. Given the expense involved and the very
low royalties you could derive from the invention (if succesful) you
should really think it through before spending money on it. The
general idea is if you think the product will produce profits
(Profits, not sales. Assuming average manufacturing profit margin of
10% you would need sales of at least ten times as much) of at least $
500,000 of which 1% would be yours to pay for the money invested in
getting the patent, you would be in the hole from the get-go. Keep in
mind that of that 1% you'd get of $5,000 if you have other income
you'd likely would have to pay taxes on.

Good luck!