Starburst2 - Here is what I did. I lost (or someone permanently borrowed) one of my lug nut covers and the nut inside on my 2011 Georgetown 350. You can find the chrome covers at truckstops but you will struggle to fine the jam nut that fits inside of the cover and then fits a 22mm stud, assuming the nut inside is also missing.
The covers are made by a company called Kaper II, Inc. I called them and ordered three of the cover/jam nut combinations for $30 which included shipping (figured I might as well have a couple of spares).
Here is their contact info and the item number (took us a while to figure out the item number but these are the correct ones for the 2011 georgetown 350)
2212 Parrott Way
Leso, WA 98626
Item # L-225
Description: Cover, Lug nut / Jam Nut Combo, for a A-225k, fits 22mm Stud
Hope this helps,