I added a third pedestal to my dinette table, on my previous RV. I found one (same length) at the Camping World store. I removed one of the screws from one of the existing pedestals, and matched the screw length for the new pedestal. Installed it and it never wobbled again.
Sorry, but I can't get to the photos of it, since my main computer is in storage.
If you tell us what model RV you have, we can better suggest how to arrange the pedestal legs, if you want to go the three-pedestal route.
Ben and Doreen
Home Away From Home - 2017 PT Crusader 315RST
TV - 2008 F250 Lariat SuperCrew 4X4 6.4 Diesel
Never Enough Time Camping!!