Craig is right about VC`s. A good resource. They are typically focused on ROI and risk. Still not a bad resource if you don`t want to assume all the risk and give up some of the earnings.
My suggestion would be to go to your banker. Do you have a line of credit? Can you increase it? OR more importantly...By now you should have a close relationship with a banker and if don`t, you should be building one. It takes time. If you have excellent payment history with your bank, he/she is usually more than happy to loan the funds necessary to a company that is "growing" and has been "borrowing and paying back those loans". If not, find another bank.
Also as a courtesy to him, I meet with my banker at least yearly for lunch and give him an update on how we are doing and what I have planned (new products and working capital requirements) for the upcoming year or three. Since he`s in the loop and understands my business, it`s easier for me to call him and ask for $100,000 for working capital. AND because I have history and he knows I have paid all my loans back, ON TIME.
I also provide him a copy of my business plan.
Another tip, when money was tight or is tight, I always paid/pay the bank first and on time.