Welcome aboard, justcramit. You can ge the Q-III from various vendors here, and I believe Amondotech carries it as well, so you can save yourself the eBay trip, where the prices may actually be higher than the ones which you'll find on the Dealer's Corner or through supporting dealers here.
As far as the Q-III goes, there are no manufacturer-released improvements, though one of our vendors here (LiteMANIA/ViKi/Warren of Vehicletech) has in the past sold Q-IIIs which he had upgraded to include mineral-glass lenses and two-stage switches. Otherwise, the only improvements made are by individual sellers who may have upgraded their Q-III at one point or another.
I believe he still has some of these HA-III upgraded versions left, if you check with him - they also had the emitters upgraded so that the performance is more 'standard' (non-upgraded versions vary in Luxeon bin, and thus have slightly different runtimes and color tints).