Original extension: https://chrome.google.com/webstore/detail/magnet-links-for-torrentz/pgmaidhfoodebfiocgananbdfnankehm
All credit goes to the author of that extension, I just updated it.
To install (before this gets on the chrome web store,) clone the repository or download here, unzip, enable developer mode in chrome extension settings, Load Unpacked Extension, and select the folder.