My son is a tad shy of 6 3 and has never had a problem getting shin guards that fit. I think his set last year came directly from an Easton rep, however in the past he has been able to get the right size at our local sporting goods store (not a chain) who will take the time to order the right size/color if they don't have it in stock.
It seems like the local sporting goods store with decent baseball equipment are getting harder to find these days
I know it costs more to go local, but it can be a real lifesvaer when you have equipment problems that need to be resolved today....and they know your name or face. Of course there are limits as to how much more I am willing to spend at a local sporting goods store for equipment and some of the stores will negotiate price on high end gloves, large purchases etc..