Niners fans looking for a pick-me-up after Sunday's brutal loss are in luck ... S.F. supporters can now nab a Colin Kaepernick jersey that the QB wore during a playoff game!!!
The threads -- which Kaepernick rocked in the NFC Divisional Round game back in the 2012 season -- just hit the block at Heritage Auctions ... and officials there tell TMZ Sports it could fetch $40,000.
Kaepernick balled out in the gear -- throwing for 263 yards and rushing for 181 more .