Medium size breed recommendations

Hello all, I am looking for breed recommendations for my service dog. I currently have a Golden but she has been incredibly difficult to work with just because of her size. The tasks I need are item retrieval, holding items, seizure response (tactical) and opening doors and stuff, DPT, mostly mobility tasks as I am in a power wheelchair. I will not be training the dog myself, my friend will but I’m looking for a breed that can do these tasks and is easy to groom but smaller than my golden. In a perfect world I’d want a small dog that can sit in my lap but I understand small dogs cannot do mobility tasks. So if y’all have any suggestions maybe for a medium size breed that would work.