Of course, buying the 2013 HTC One Unlocked Edition now is not exactly a wise thing do to, as the 2014 HTC One will likely be released shortly after its announcement, possibly as soon as early April. The new handset will probably be a bit more expensive, but perhaps the improvements that it brings are worth the higher price. Among the expected improvements we'll mention a larger display (5 inches), Android 4.4 KitKat with Sense 6.0 UI, a quad-core Snapdragon 801 processor, and a dual-lens rear camera.
Anyhow, if you still want to get the older HTC One Unlocked Edition, this can be purchased online from HTC, and it’s available only in the US. Check it out at the first source link below. Apart from being fully unlocked, this variant of the HTC One is identical to the regular model that can be seen in this gallery: