Buying the track directly is the most reliable way to own a permanent MP3 file.
You can purchase the individual song or the full album Death of a Bachelor on the Amazon Digital Music Store. Once bought, you can download it as a high-quality, DRM-free MP3. House Of Memories MP3 Download
If you have a Premium account, you can hit the "Download" button on the official song video to listen without an internet connection. Safe Practices Buying the track directly is the most reliable