Yeah, sometime after 8 am on Day 3 the back door of Kokonutz Sports Store will open, if there are too many survivors active this won't happen. What I usually do is kill the 3 Poker Players in the televised playing room in the Atlantica and as long as there aren't too many other survivors you should be able to enter the back room now. The one guy needs a Cement Saw (Found right by the maintenance room by the Yucatan and Garage entrance) and Plates (Found in the sinks of the Luaii Wauwii Restaurant) Make sure NOT to combine them before giving them to the guy who needs them and bam, Combo Card. Just make sure you're back by 12.
Additionally, just before the military arrives, you should get a call about the Tape it or Die people again and if you save them, one of em gives you the Blazing Aces Combo Card.