The Microsoft Portable Power DC-21 is an external battery pack that's so far been sold for $49. It comes with 6,000 mAh of capacity, which means that when full it can charge almost any smartphone out there at least twice. And no, the device you charge doesn't have to run Windows 10 or Windows Phone for this accessory to work.
So, the good news now is that if you want one of these, you can get them for just $24.99. That's almost half price compared to the amount charged before, thus this is a pretty good deal. The Microsoft Portable Power DC-21 is available in three colors: white, orange, and green.
You can pick one up from the Microsoft online store. Charging the DC-21 itself takes around four hours (or three to reach 80% charge).
Since this is likely to be a way for Microsoft to clear its remaining stock of the DC-21, if this deal seems interesting to you, perhaps you should take advantage of it as soon as possible.