no idea about cheap chinese custom glass...
but i think i remember reading that you are from germany? check out zenit bongs, they do custom work and have skills. it may not be the cheapest option but you have no hassle with customs (zoll) and you support your local glassblower
if you get your tube, make sure to post some pics
also ssfg comes to mind, they have experience in making hydratubes and are on the more affordable end of the scale, but of course us-based...