Promo Game Time Arrival

Hey Stros Bros and Gals, long time lurker (I get all my info about our Astros from here), first time poster. I am taking my Mom to the game on Sunday because she really wants one of the scarfs that they are giving away as a promo. I would like to know, how early should we get there in order to assure that we get the promo.
Thanks in advance for any info!

As i stated above, first time poster, but I love this sub and all the great people in here.

GO ASTROS!!!!