Far as I know not all seals you get from suppliers are the old food grade ones that were used originally. Most of the new ones are the same material that you can get at the plumbing store. I believe they are called Buna-n. Size As568a Dash number 109, 111, and 417. I bet they are called something different there. Not sure what the old food ones were called. Our new store has them and we talked about them, just did not stick.
It would not bother me to get them at a hydraulic shop if they had ones suitable for drinking water.