i would look at this thread :http://fuckcombustion.com/threads/joda-glassworks.13915/
And contact Vaped&Confused, he will make you a custom stem, with all your specifics and give you a quote.
Also, Planetvape.ca has some custom stems that i find much better then the stock. Though they are not longer except for the PVHE Vortex, found here: http://www.planetvape.ca/pvhes-high-efficiency-vortex-stems.html Which is brand new, and ill be giving my opinion once i get it tomorrow.
All very Solid advice.