That's true. UM used to do one-off requests, but I guess they've gotten too big and are unwilling to do such a service (although they might be willing to make an exception for you if you make it financially compelling for them, though I have no idea how much that would take). Master Xiao of Gui Ling is pretty experienced; he designed most of the Rooth product line --- he only left Rooth and went back to his hometown for personal reasons, so he's still amongst the best regarded designers in China. Still, the request can't be too crazy. Gui Ling was the only one willing to do special combinations for me, though the combination I wanted was actually pre-worked out by me and had a pretty safe likelihood of succeeding.