The way to find investors is to ask around. Ask your friends, family and colleagues for referrals to people who are known to have money and may be open to unique investments. Filmmaking is a high-risk investment but it can pay off if the film makes enough money to pay the investors back. And usually at a high rate of return.
You need to find those investors willing to take a huge risk on your project as they may never get that money back. These investors are not easy to find but they are out there. It takes a lot of time, patience, and willingness to ask people for money.
If you don't have the contacts to those with money or the thought of approaching others for money makes you sick to your stomach, don't give up. Think about finding someone who does have those contacts and the outgoing nature and see if he or she would like to be an Executive Producer on your film. They can be in charge of approaching their contacts for the money. This person may be an accountant or lawyer or a professional who interacts with others with money.
I don't know of anyone who has had much luck with venture capital when it comes to investing in film. Venture capitalists like big investment opportunities in fields they understand. And most venture capitalists don't understand film. And what they don't understand, they don't invest in.
In addition, I don't recommend the cold call. The best success is a referral from a trusted source to an investor. So focus your energies on your contacts who may be able to introduce you to other contacts with money.
Once you have some referrals or even one referral, present them with a business plan that explains your film and how the money is going to be handled in the film. This is a business and you should have a plan that treats the money in a professional way.
If you don't have a business plan or even a company for the film in which the investor will become a member then you should take a few steps back and spend time educating yourself on how to open a company and craft a business plan for a film. Entertainment lawyers or other producers can help guide you appropriately.
Then get out there and turn over every rock you can find and then find more rocks.