Thanks,
I found what I was after...
There seems to be three different sizes of welt 'bead' out there: 3/16", 1/4" and 5/16".
The 5/16" rubber is what I got. It looks great even if it is a bit larger in diameter. It is smooth (not like the textured vinyl) and is easy to 'work with'.
No big deal...just in case someone goes searching the archives on this subject.
Hot rod shops sell it and the old **** truck parts places have it.