First of all, thanks John and Joe.
I have learned two things on this search:
1) The nut I am looking to replace is called a jam nut,
2) the wheel inserts I was trying to decribe are called wheel simulators.
Anyway, went to the Lazydays RV dealer without the nut, and the person had no idea what I was talking about nor did he believe anyone but the mfr could get the suitable replacement.
Went back to the same Lazydays with the nut from another wheel. Well, the part in hand and a different rep, and I had a replacement in hand in two minutes. He asked me if I wanted more than one, and I said four just in case. Well, when he told me they were $20 each
, let's just say I left with only the one I needed
.
I still don't have the stainless lug cap that goes over the nut, but not the main concern at this point. All of the caps I have seen are 1.5", and the one that goes over the nut needs to be slightly larger, like 1-5/8".
Anyway, thanks for the help.
Brian