The labels that I have printed for my Systainers and also for "My Piggies" have held up well and stay stuck in my experience.
If you go to onlinelabels.com
you can choose the media type. My labels are the weatherproof poly laser. Frankly printing weatherproof on an inkjet is silly. The label will stay stuck but the ink will run. But, that is also an option. For classic systainers I used the OL8250LP which is 8 labels per page and did my layouts in Adobe Illustrator.
The Festool program for the T-Locs does a label image that is 3 3/8" x 2 1/8". The issue is that you can't really move it around to meet a label template location, so you would have to order full sheet labels and then cut them out. Lots of waste.
That size is pretty close to a business card and the new T-Locs have a recessed place that allows you to buy a plastic cover and just slip plain paper behind it - like Brice said.
If you want to go the label route I would suggest that you try out printing a test label on paper and then run it thru again and again and again trying the various positioning options available thru Adobe Acrobat Reader. I think that it is conceivable that you could print between two and 5 per page if you re run your paper thru the printer.
If you order from the link above you can order as little as one sheet but the cost is pretty out there versus purchasing in a slightly greater amount, so check that out.
Sorry I couldn't help more. I would play around with some stuff but my plate is full and I would have to get permissions etc.