The Minyami Extension isn't available for Firefox, so I converted it into a userscript. Just install it and on supported sites, you can click on the userscript manager icon and you'll find an option "Download" beneath the the script name "Minyami". Click on it and the download command will get copied to your clipboard. The script also tracks all found download links to enable bulk copy of download commands. You can add more sites yourself if you edit the appropriate sections of the script.

All credits go to Last-Order, I just put it into a userscript.