Finding B2B Opinions and Earlyvangelists

Hi, I have a product vision and minimal prototype for a SAAS (or not) product to be used by software development teams. In most cases the economic buyer would be (in the case of a SMB company) a development manager (in a larger company) a director or higher. I know that I need to get my product in front of these people to verify if it is something they will part money with but I have no idea how to get in touch with them. I have read lots of good books on product development, customer development and the like. But I think most authors assume that the boot-strapper has a rolodex filled with contacts in the position to purchase their product. What are some actions that can be taken to locate and approach people in a B2B setting who will hopefully become earlyvangelists?