Most machine manufacturers would have ‘usually’ engineered and designed around the use an off the shelf bearing for the inside bore and outside diameter. It’s still seems to be growing issue in some cases like Phillip’s where there just not being manufactured anymore. There’s still a surprising amount of of new / old stock bearings around as Andrew mentioned though.
I’d start with putting some time in and running searches using the bearing number code and you may just get lucky. If your not, then your going to have to get creative and re engineer the original design to use something that can be found today.
However, I got curious about your Elliott pillar / dill press and found this video that might be of some help? https://www.youtube.com/watch?v=CpGharWWOjY&t=14s That video is from last year and at least at that point he was able to buy replacement bearings. The full list of bearing numbers is in the video description.