There are tons of arduino based clones from $2 up to 30 some even with more features, like dip switches to choose wich script to run or even wifi capabilities. There is also a code repo on github with the code needed to make some of these (around $10) run regular ducky scripts, and a "translator" to convert ducky scripts into arduino code. You can use even a regular arduino (not all of them), or a modified pendrive to do this.
BTW, nice article. It's a ton of fun playing with this things, and a lot of people don't even know this exist. I started using them after hearing about cheap alternatives at a hack and beers conference.
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