Master Lock Padlock, Set Your Own Combination TSA Locks for Luggage, Travel Zipper Lock with Cable Shackle is 1-3/16 in. Wide, Colors May Vary, 4688T, 2 Count (Pack of 1)

I use Ski Tubes a couple of times a year with my family of four and have never had any problems using a TSA approved lock - I was concerned the provided clip would not be replaced by the TSA (as noted elsewhere) and without something holding the two halves together your Ski Tube will arrive in two pieces. I use a lock like this one: https://www.amazon.com/Combination-TSA-Approved-Luggage-Lock-Flexible/dp/B07K7XJBV8/ I've had problems with the interior velcro that holds the skis in place separating from the strap, but otherwise have not had any problems with my gear packed in the Ski Tubes and this has included travel from the US to Europe (with stop overs) and domestically.