First of all, your sex partner is right. He is not obliged to help you financialy just because you fucked. And I don't see what is regretfull from your side, as long as you enjoyied fucking him. Had you not done it with him, you would be at the same spot, except you wouldn't have some pleasant nights to remember.
That said, since it's obvious that you aren't really bonded to that man, on a spirtuall level that is, don't you have any close friends or family members?
I can see my self denying giving money to a random girl i fucked but i would never deny help to a close friend, a close family member or obviously, a girl i have a deeper relationship with.
Also would you help him if he was the one in need? And if you would, does he know it? Because i also wouldn't help someone who i don't think they would do the same for me