First - thank you for your service!Sorry to hear you are having issues as a result , just wanted to express my appreciation for what you do and the risks you have taken.
There are trainers that will evaluate and train an existing dog. The key word is evaluate . Good trainers are pretty strict about who they will train as SDs. The dog that becomes an SD represent the whole community of SDs , dogs that obviously have behavior or personality issues that are wearing vests damage the reputation of true SDs..hence good trainers having strict requirements about what dog can become a service dog in training .
All the agencies here have a 2 year plus ( up to 3 year ) waiting list. You can go private , but that still does not mean they will have a dog ready ..and even if they do you will need about 15 to 30 K depending on your specific training needs.
I searched and searched for an 18 month to year old dog that would pass the evaluation . I did find one temperament wise , but he had a real wet mouth ( a Corso ) and any good trainer would not call a dog that slobbers a lot a candidate. He needs to go to restaurants and such !
In the end we took a gamble because a rescue I am friends with found a pure GSD who at 3 months old appeared to have a good sound personality . The trainer I am using was pretty specific in saying there is no way to know at that age if they will make it , because there are too many typical stages to go through yet ( fear , etc) ..and you can't tell if it is a stage or not until they are a year old or so. I suspect any good trainer will tell you the same.
We are taking a gamble , our pup is about 6 months old now , and he is doing great. We just finished Puppy Kindergarten .. we will do Intermediate , Advanced , and CGC. Once he is a year old..about 6 months for now , we will have a better picture if he will get his "in training " vest and start officially.
If he does not make it..if he develops issues or whatnot or just does not have the drive for it , we will still have a well trained loved dog for my son who will make our lives easier and better ( he already is) . We just won't be able to take him everywhere legally.
Another reason we wanted to go private training and find our own dog is because the agencies wanted me to rehome at least one of my other 2 dogs .. and I just could not do that .
As for raising our own potential pup , we are doing some things differently than we would with a pet dog , right from the beginning , so that is also something you would want some trainer guidance on. For instance , he sleeps in bed with my son. That is not something I would allow a pet to do . We are also rewarding when he barks at a door or up the steps when my son or one of us leaves the room..eventually he will be trained to alert when my son is sneaking out .Again , barking after a family member that leaves is probably not something I would have encouraged a pet to do.
SO , do a search on service dog trainers in your area ..check FB pages in your area ..that is how I found my trainer.