The 49ers are putting some individual tickets on sale on Ticketmaster at 1:00pm PT for Sunday's NFC Championship Game. Unfortunately, it appears as though no more than 100 tickets will be available. There were fewer than 1,000 available for the last week's divisional round matchup, so this is not particularly surprising. I'd recommend still trying to log on for tickets, but don't be shocked if you can't get any through Ticketmaster.
If you are looking for tickets for Sunday, there are some secondary ticket options. The NFL Ticket Exchange is the official NFL secondary market. Niners Nation has an affiliation with TiqIQ. Stubhub is an option and of course, there is always Craigslist. If you do purchase tickets through a place like Craigslist, watch out because counterfeit tickets are all the rage for big events.