There is not part number or anything but it is a wheel that goes into a grove at the top of the door. It is attached with just a screw. No nut. The inner part of the wheel is the nut.
Casey from SWISCO responded:
May 14, 2019
Good morning,
It appears you have a flat, 3/4" nylon, ball bearing wheel, so take a look at our 10-141. Compare it to your original to be sure it will work for your application.
A home owner from California says:
May 14, 2019
Thanks Kathleen
The only difference I see is 10-141 is for a shower door and mine is for a screen door. The wheel for the shower door is a solid wheel while the wheel for the screen has a grove in the wheel. It does not seem like it needs that groove but I can not tell by looking. But I will give it a try as I have tried others and this looks closer than most. Thanks.