Interesting! I make my own labels but it's a bit of a process.
To make mine, I make them in Microsoft Publisher and print them out. Then I cut them out. Then I spray both sides of the label with clear spraypaint (one side at a time of course...) to make the paper labels waterproof. Then I stick them to the fixture with weatherstrip adhesive, which is very nice aggressive adhesive. Works great and doesn't cost much. But if you don't have the patience for it and would rather spend the extra bucks for real-deal labels, seems like you've got some good outlets to do so.
I've been able to create exact copies of a few NEMA tag designs by the big three manufacturers. Would be cool to get them printed on vinyl!
There is a minimum order of 25... Do they have to be 25 identical labels or could they be 25 of the same size/shape (3" square) but with different wattages and sources? Would be a bit of a waste to order 25 of the exact same NEMA tag but if I can get a variety I'd certainly do it!