A lot of places have community clinics that offer income based prices for medical services. The three places I've lived (mind you, it's not a very geographically diverse three places) have had clinics of this sort, so there may be one where you live as well. They may or may not be able to perform it, but if they can't, there is a good chance they can point you in the right direction to get it done with your income level.
If you haven't already, I highly suggest you look into these clinics.
If you haven't already, I highly suggest you look into these clinics.