There were two exterior trims on my Argosy. What I call the midline trim, it is about three feet up the body from the bottom, and the beltline trim that is on the bottom right before the curve to the belly pan. My midline trim had a 1" or so fiber board insert that was painted a yellow or gold color. My belt line trim (lowest trim) has no insert. Both of my trims are made from aluminum.

I deleted my midline trim upon repaint mainly to keep from sourcing the insert and secondly because the trailer looked better without it. I had decided that if I was going to put the midline trim back on that I was going to cut sheet metal for the insert. Had pondered going to a home rain gutter company to have them cut a continous strip for it. Vintage Trailer Supply offers a blue insert that may or may not fit the Argosy line.

If you post a picture of the trim you need it would help me clarify exactly what you're looking for.

I hope this picture went through

It did! So your lower trim is different than mine. Mine isn't made for an insert like yours. Vintage trailer supply has what you need. This link should carry you straight to it. If not go to vintagetrailersupply.com and search rubrail.

http://vintagetrailersupply.com/Black-Vinyl-Rubrail-Belt-line-Inser...