Oh, such abuse a poor girl has to endure to get her film made! Don't be offended, Darla, just consider it mild preparation for dealing with the distribution phase.
On a serious note, could you negotiate a fixed price with your DP that would be enough to entice him to do the work? If so, then you could go out and fundraise for it. Depending on who you know and are related to, a good way to raise modest amounts of money is to send a nice letter to your entire friends and family list explaining your project and asking for donations. Be specific and say "I now need $XX to pay for YYY part of the project." I'm personally terrible at asking for money, but the few times I've done it, having a specific amount for a specific purpose has been more successful than a general request.