There's no tab that I've found, but there is the Jerry Garcia Songbook. This has the chords and lyrics for basically all the songs Jerry ever played.
What I did was vamp the chords to get the changes down first. Then add in rolls that fit and match the rhythm. Forward-Backward and Alt-Thumb rolls work best for this song. Don't be afraid to use rests to give it good rhythm and accent the notes you do hit.
You can work out the main lick using the guitar tab in the songbook and modifying it for banjo, and play that between verses. I never thought a lead solo break worked well on banjo for this song, and it's mostly a lyrical song anyway so just focus on good rhythm and singing it well.