Lots of people do liposuction. You're already engaging in risky behavior. At least consult with a doctor and get a quote on the price. I don't think that's very expensive to get a consult and set and manage some expectations.
Not sure what a "nice looking stomach" means. A assume at least flat, at best you can see some abdominal muscles. But I seriously doubt any injections are going to target and remove fat cells and not kill good tissue.
From what I understand if you want a flat stomach, you really need to get your body fat percentage into the single digits. If you were there now, in the single digits, and then considering injecting unicorn piss to burn fat locally, it'd be one thing. Is your body composition in the single digits for fat percentage? It doesn't sound like it from what I read.
But hey, it's your world and your body. Do what you want.