I knew I needed a service dog so I consulted the trainer I told you about and she advised different breeds appropriate for me and my needs and size as well as breeders.
I suggest finding a dog trainer (that trains service dogs) and conveying your needs and size info so they can help you with your choices. They could probably help you with a breed or selection of choice.
If you train the dog yourself, please remember it will be at the minimum a year before your pup will be ready. If you get a giant breed, it will be two years before full service is possible.
You can get help with funding. I received mine through Wyoming Independent Living and you may find some through different state disability assistance groups or foundations.