Have you looked into it yourself? I used DAV and they were a useless shit show. I reached out to the American Legion, and got little to no response. Decided to do it myself. Did my research, asked around, and won several claims and appeals.
A lawyer is the easy route, if you don't mind losing a cut. But if you have some time and are willing to apply some elbow grease, depending on the claim, you might be able to DIY.