A starter will survive in the fridge for three weeks, so I wouldn't worry about it in the first place. It might just need a few more feedings before it's ready to go again.
If you really want to take it along, just feed it up, put half of it in the fridge and half of it in some suitable container for your suitcase. If the TSA doesn't find it or bother about it, you can feed it, bring it back home and toss the fridge one. If they take it from you, you always got the fridge starter.