Tizio Classic Desk Lamp?

I own a Tizio Classic desk lamp and need to replace the large pivot located on the lower portion of the arm which had been removed when the thermoplastic cover broke related to age and was removed when the lamp required servicing but not replaced due to lack of a part. I have been able to obtain the 86mm pivot from Amusesport in Nevada but the problem I have is how to remove the snap joints and replace them with similar snap rivets? I found a reply to a similar question dated September 2019 by a gentleman named Marcello. I hope he would be kind enough to identify the size of the part from Prym and to carry out the replacement. All help