The Mimi Fishman Foundation’s latest on-line charity auction is underway. Tickets for each of Phish’s four shows at Madison Square Garden on December 28-31 are available. In addition, an extensive array of signed posters is part of the auction. These include a Pollock poster package, which collects all three of the artist’s posters from Phish’s 2010 shows at the Greek Theater (signed by Pollock and the group) and all three have matching numbers. Bidding for all of these items concludes on December 1.