does anyone know of a brand that makes such a stem, 140mm length with a 0 deg. rise/drop?
I assume you mean 90°, 1-1/8 steerer and 31.8 clamp ?
140s are hard to come by in general. Although I'm some obscure brand makes a 140x90°, I couldn't find one for myself and tried a 140x86° Deda Zero100. I didn't have enough steerer and ended up swapping my bars to 26.0. Plenty 26.0 x 140x90° stems exist used or NOS.
140mm x 90° x 26.0
- 3T Forma for 1" steerer (I believe they also made a 1-1/8")
- Thomson Elite (old style) 1-1/8 steerer
- ControlTech single bolt bar clamp with thread inserts (the good ControlTeck stems) think it's 1"
- Salsa welded steel, 1"
140mm x 90° x 25.4
- Syncros hinged, 1"
- ControlTech as mentioned above but in 25.4, 1-1/8
135mm x 90° x 26.0
- Salsa Moto Ace, 1-1/8
and a bunch more I don't remember, all buried in my parts boxes.
Here's the instructions for the stem. This pdf is before the 4 degree stem was offered, but im sure you can figure the math out. -4 stem with a +4 shim is zero.
As hard as you can.