If you don't know any investors or people who know investors, start with your family and friends. They know you and are more willing to take a risk with you than someone who doesn't know you.
I once asked an angel investor when the ideal time was to come and ask him for money. He told me "when you don't need me". If you can do anything to get closer to generating revenue now, even on a small scale, you will be in a much better position when you go to raise money.
Surely a working prototype is something that you can ask people to pay for. And even if you are not covering costs, getting money in the door will cover SOME development costs and help convince someone else that people will pay for what you are building, which is the only reason they're investing in the first place.
It is probably perfectly possible to locate customers if you have a prototype, depending on what you do.
Don't underestimate sales.
With the economy tanking you'll soon have enough of both. Is it possible to open source enough of your concept that you could get community interest, but without losing your value-add?