I am in the process of contacting potential supervisors for Post-doc position and I need a bit of advice on how to reply to one of them. I have a PhD in urban planning and I am applying to some American Universities for a Post doctoral. After contacting to a supervisor, I got a positive reply, however he wrote to me: "You have impressive credentials, and I'm sure you could contribute  to  our group. However, I have no additional funds at this point to support a post-doctoral position. I would be happy to talk if you have funding from another source. But at this point, my funding has been allocated to ongoing students. I am sorry that I do not have better news."

What and how should I reply? On one hand having some financial support is quite vital to me, but on the other hand I don't want to lose this opportunity.I would like to show how much enthusiasm I am to work in his group. I would like to suggest to write a proposal in order to give a grant, or asking him if he know somewhere I can find a financial scholarship. or I ask him let me know when he has a vacant position for me.I am unsure what to do!