Have you looked into the tucker sling? It seems to work well and can be covered by insurance. Other than that, maybe a re-evaluation of his meds to see if there's something that can be done to make him more comfortable. ??
As the mom of a persistent "refluxer" I've tried numerous things to comfort my son. He liked weighted blankets that could also be warmed in the microwave. You could probably make one from an old pillowcase...maybe make 4 or 5 sections starting from the bottom going to the top (lengthwise). Put a little flaxseed in each section and sew across. Repeat that until you get to the top. You don't want to make it heavier than 10% of his body weight.
Reflux isn't easy to control in a little one. It's not because of something you did or didn't do. In my experience going to a chiropractor won't make reflux go away. The best thing to do is to keep him elevated (app 30 degrees), find an antacid that works (we use prevacid) and try to avoid foods that trigger the reflux. I would hope that he grows out of it soon, but you may need to look into additional testing down the road if you don't see any improvement. My son got his medication through an ENT initially, but it's now from a pediatric GI.