Where to find a manufacturer?

I have an idea for a simple invention made of plastic that is relatively small compared to most things. It isn't by any means very complex. But can someone point me in the right direction to find a manufacturer or someone that can produce such a good? Considering I should be looking for a manufacturer and not another producer in another field, that has a more technical name

depends what you are doing if it is plastic can it be made through injection molding? If you are in the US its going to be very hard to work directly with a manufacturer without having a prior relationship or having engineering specs on how to make product and have it patented. but do a google search plastic injection molding manufacturers in the US and see what you can find.