Need new casters

Hi. I've attached photos of the caster that I need to repair my sliding glass doors. These are on a boat...1971 Grand Banks Laguna. I don't see any markings on the part. Can you please help me identify it? I'll need 6 of these.

I have images of it installed into the door, also but I can only upload 5 images.

Thank you so much. Please contact me at leonw2@hotmail.com or 323-440-4734

Best,
Leon