"afraid the public defenders office is not going to help much"
And where do you come up with that? PDs have lots of cases, but they are usually highly competent attorneys. Your son apparently doesn't even have a PD yet, but you already believe he'll be a dumptruck?
There is some myth out there that there are pro bono attorneys. There are attorneys who take individual cases because they are kind, but they certainly don't advertise. Attorneys have bills just like everyone else. Actual pro bono attorneys normally work for large groups with a unified that receives lots of donations. ACLU, NRA, AARP, etc.
Best way to find an attorney is word of mouth.
Be thankful you're in a country that provides free legal representation, instead of just shooting people out behind the courthouse.
Free Attorney? No. Free ice cream? Yea!!!