Texas

If I understand the official guidance, boosters aren't needed unless you got your childhood vaccine between 1968-1989 since that's when they used a less effective form - otherwise you should be 95% protected throughout your whole life. If you need a booster then I assume you could ask your PCP and they would probably be able to direct you.

I got mine at my doctor’s office. If you don’t have insurance, you might call Your local health department to see if they are offering them. Or check with your pharmacist.

Note it might be more effective to get a titer test from the doc vs getting a unnecessary booster a titer test is just a normal blood test and is a lot easier to check vs getting another vaccination that could go to some child that needs it.