It is not entirely certain that this gig happened. As far as we have been able to find, the New Riders hadn't been billed for a gig since November 29, 1969, and wouldn't play again until March 18, 1970. What were the New Riders doing these months? We don't know. But all of it does seem to make this one-off gig unlikely to have materialized. On the other hand, the announcement in the Friday Daily Cal makes it seem more likely, and that piece even anticipates Philip Chapman Lesh on bass.
mention: Berkeley Tribe, January 16-23, 1970, p. 28
announce: "Jerry and Friends for CEC", Daily Californian, January 16, 1970, p. 11: calls the NRPS "a pirate version of the Grateful Dead" and namechecks Phil Lesh. This gig, and the putative March gigs, might be Lesh's only NRPS gigs, but that remains speculative.
listing: San Francisco Chronicle, January 19, 1970, p. 36