I don't have much to add, but since he mentions the New Riders of the Purple Sage gig(s) from August 1, 1969 at the Bear's Lair, UC Berkeley, I though I'd post some scans that I have.
I especially like the one above ... "Jerry Garcia with Marmaduke", but the picture shows Jerry and Mickey Hart.
A few notes from all of this.
1) there seem to have been two shows, at 8:30 and 10:30
2) Mickey Hart was on drums (no surprise there), but as Corry notes we don't know who played bass. I'd have to guess Phil, but it's just a guess.
3) they appear not yet to be called the New Riders of the Purple Sage, though that's how I'll refer to this. As Corry notes, it's not until the end of the month that this name appears *anywhere*.