Go to your bike shop or an online store and order the most expensive "bits and bobs" - it's all commercially available, and for the very reason you would think (person sees a pro use Shimano Dura Ace Di2 drive train, thinks he too can be like the pros and buys it for his own bike). As for their used stuff - whatever isn't all broken and worn out most likely gets transferred to another frame or back into the parts bin it goes for a training bike