Antabuse can be a wonderful tool, and like all the medications around that can help with substance abuse I feel they are massively underutilized.
I'm not sure you'll be able to get it from a walk-in clinic. My primary doctor prescribed it to me, but only after doing liver and kidney tests. Antabuse on a healthy liver poses little to no risk, but if your liver is struggling, it can be quite dangerous. Also as other's have stated, many people continue to drink while taking it. I specifically asked my doctor to prescribe it, as I'm emetophobic (fear of vomiting) and knew it would stop me from drinking. I always urge anyone looking into medications to talk to their doctor about all your options. Naltrexone has been shown to help a lot with cravings for alcohol (and opiates) and Acamprosate can also be very helpful for some. Of course, all of these medications have a better chance of helping if you are also receiving mental and or chemical health services.
I hope you find what you are needing. It's always a good idea to have a primary doctor and to stay up to date with annual exams. Maybe get that scheduled (even if it's with a new provider) and talk with them?