How fix sliding glass door?

My house has a sliding glass door on the patio that barely moves. The door and fixture it slides on look fine but it seems the wheels or what ever it slides on do not slide at all. I can budge it with a lot of force. I asked my handyman who renovated the house very well to fix it, but he said cannot find the parts. The house was built in 1958 and the walls are made of cinderblock but I think on the patio it is just wood framed around this door, not sure. How do you think I could find the parts to repair this? Or how could I find a person who knows how to get the parts and repair it? It is a rental far from my home so I can’t do the work but I want to hire the right person and that is a unique person becuase my very competent handyman can’t do it. Thanks for your advice.