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This whistle fights fascists | How thousands of 3D-printed whistles are derailing ICE.
(www.theverge.com)
This is a most excellent place for technology news and articles.
You can do it with any 3D printer, as long as you orient the letters so they're at the top of the print, you can insert a pause in the print job just before it starts the layers with the letters. Then you do a manual filament swap and resume the print.
Another option is to print a QR code on them with a link to instructions/the organization.