Office chair repair place sought

Maybe a long shot but my Okamura Barons Mesh office chair rigid seat cushion popped off the rail on one side during a move and I cannot put it back in. I tried to pry it and force it but the plastic is to thick to give in. I bought it second hand at the Office Busters in Matsudo but that location closed permanently. Is there a place that can fix an office chair? Thank you.