I'm going to try this:
NCAA March Madness Live
It's clunky and they might limit how much time you have (they have in the past), but if you have no other options, go for it.
I'm debating getting Sling for a month (I subscribed for it back during football season), as well, but annoyed I'd only get TBS and TNT in the base package and I'd have to dish out extra for TruTV. Seriously, why is TruTV part of the lineup? It's such a random channel to broadcast sports.
To coincide with the first games of the NCAA Tournament, known as March Madness, Sling also added Turner channel truTV to its $5/month Lifestyle Extra pack. The channel will carry numerous games, starting today.
TNT and TBS, which are available in Sling's base package, will also air a wide selection of games starting Thursday, March 19. In total the three Turner networks will air 49 tourney games and cover the first three rounds, as well as select regional finals and the two Final Four games on April 4.