I am new here but I did manage too sell one of my ideas and it is now patented, I receive royalties for it. All of the suggestions are good and places too start with. I will list how I did it and maybe it will help. I first made the item, or prototype and then used it in the field. In my case it was a siding cutting table. Then I paid $120 bucks for a provisional patent (now this is good for a years time). I then sent out various emails with pictures of my item and did allot of phone calls on top of it.
Out of all the contacts only one responded and that was six months later. So never, never give in too despair. It can and will happen sometimes it takes time. But my provisional does protect me from rip offs and it gave me many opportunities too visit other manufactures. Another thing I want too point out. You have too ask yourself is this something I want to manufacture and receive all the funding for? Or, is this something I want made for me, (packing, marketing, advertising, sales, ). I chose too receive only the royalty. Good luck with your idea. Hope this information helps.