Have you thought about asking DSIL or DB if he is willing to part with any of their Harley t-shirts or bandanas?....might be something special that he would like in the quilt too? Just a thought?
or you could check out : www.harley-davidson.com
they may have something available that you could use in the quilt? I know they sell their own embroidered patches, fleece blankets, clothing of all kinds, bandanas, doo rags, etc.
Hope this helps!
DeeDee