Thomasville Dresser 1970

I am looking for the plastic parts that the drawer glides over so the wooden drawer is not rubbing against the wooden frame. They are the dark brown circular plastic pieces shown in the pictures. In the first picture, you can see them both in the second drawer opening. They are completely missing in the 3rd & 4th drawer openings and there is only one on the right hand side of the drawer. Would you have any idea where I can purchase these replacement parts? If there even available? Thank you and have a great day!

Lopaka