OK - It's been a while since this topic was last posted too, but... I have Summit 650 (2004 vintage) and I think that it has the same caster insert and wheel. There is a 3D printer part posted on Thangs courtesy of John McConnell. Search for "Old Weber summit gril caster holder" on Thangs. I used it to replace both caster inserts for our Summit 650. Cost was about $40 per piece to have them 3D printed from polycarbonate filament (PC). Grill resides in Arizona, and despite being 20 years old, it's still in pristine condition - did not want to have to stop using it or go with a jury rigged solution for wheels...It's too early to tell how they will hold up, but sharing this option with everyone, because $80 to repair the grill is a whole lot less than $3,500 to replace it.
Photos of the printed parts below...
