The link you gave to Meridian has them in packages of 8. Do you think those won't fit the ID of your poles? I have bought multiple times from Meridian and always have been quite pleased. I even bought an 8-pack of these very inserts too.

If that doesn't work though, check with Dennis at Dobstuff. He has inserts of all sizes. I would expect the Meridian 8-pack to be fine though. They're likely the same inserts as McMaster sells anyway.