When our company was starting out two years ago we sent out a mailer, a letter of introduction, to 300 or so local GC's, and recieved responses in similar numbers to Active 1. Even without any telephone follow up we had about a 3% to 4% response, and about 1% turned into actual customers. One of those customers we did almost $100,000.00 in business with last year. A pretty good return on investment for $150 in printing, envelopes, and stamps.
The source for our customer list was just a list of GC's from a local business association that we found on the web. Yellow pages would probably work just as well.