I bought one from Miller's last fall. I think they had three left. They were NLA at MB Classic Center.
Give Miller's a call and describe the part. 1 (800) 338 7787. I had no problem. I just told them I was looking for the chrome "thumb nail" that covered the screws on the chrome door locks.
I have a receipt that may be the cover but it just says "Edging" Item # 42-0029. I believe they were $39/each.
Lucky for me I only needed 1. I had the other three re-chromed ($20 total)
Norm