I don't use it, but I definitely assume this to be possible.
Nevertheless many members of this forum use the "Forumslader" for permanent power supply at bikes. If you understand some German you may find all information at www.forumslader.de
Basically there are two reasonable options. The first one is to build the older version called "12V mit USB" (or similar) by yourself. You can get a prepared plate from our forum member JensD or design your one one. The electric circuit plan is one the aforementioned web site. This option is much cheaper and more flexible concerning the batteries, but requires skills to build the Forumslader by yourself or someone else.
The second option is to order the latest automatic version. It is based on SMD parts and is designed so tiny to fit in the AHead stearing tube (but might also be build up for nonpermanent use at the bike). It comes almost complete, but you may figure out the details with Jens directly. It is more expansive (we talk about the range 100-200€), but definitly worth the money. The latest version even comes with the option to use it as cycle computer (via bluetooth to your smartphone) inclusive altitude functions.