Welcome to the forum. If you search "airport," you should find companies that are often begging for shoppers who are badged. Since you get to skip the Gropers, maybe you could show up a little early for work and knock out a few.
Try signing up with Customer Service Experts, Ath Power Consulting, Shopper's View, and Shared Insight to begin with. You can also go to PrestoMap.com and look for airport locations.
Not mystery shop related (well, tangentially), but have you seen Soarigami (http://soarigami.com). It's an airline armrest extender invented by a former MS VP.
Now scheduling travel shops for the day after Christmas through mid-January.