Global warming and climate change
Over the last couple of days, I've ran across some articles showing the amount of people who believe our world is threatened by climate change. It's well known that most, or all of the countries who made commitments in Paris are falling behind their promises, and more needs to be done. For people who want to show their support for a changing world and a more sustainable future for generations to come, there is an interest in novelty items such as mugs, key-chains, T-shirts, etc...
Yes, there are a lot of people who do this already, but that doesn't mean you couldn't either, if you're crafty making any of these type of items. They could be sold practically anywhere offline or online. Since there is a lot of interest in this topic, your target market is huge. What could you have printed on them?
I ran across an article on a Yale University website that shows the results of a poll they did last year. Any of these captions from the poll would work. You can see the amount of support for each.
If you wanted to be a little more proactive you could locate environmental groups on Facebook, and tailor your items towards their cause and offer to split the profit with them. Some of these groups will be paying for lawyers, consultants and many other things to further their cause, so a means of generating income to help stop the drain on members wallets, could be very welcome. You could buy bulk order screen dyed T-shirts for likely under ten dollars, and have the group sell them for $20. You make $5 and they make $5, except they are doing all of the legwork promoting and selling them for you. That's worth a lot.