Greedy Shade, Pandemonium rare nanos vendor is just on the "roof" of save point in Pandemonium Garden.
Pos: 337.7, 384.1, 128.5, Area: Dante's Sanctuary
Edit: he has also been spotted at 326.4, 388.0, 121.7 behind the save point on the ground, and on a pillar nearby. So maybe his spot is altered when the worldmap is reset by an update?
Remember, you don't need a key to enter Pandemonium Garden. (You still need Pandemonium access, of course.)
This vendor sells more than normal nanos ... you can also buy the "Weird Looking" nanos that upload "Improved" versions. These nanos still have the (2%) failure rate. The difference is you don't need to farm or wait for someone else to farm them. Costs on nanos can be in the hundreds of millions for some nanos BUT a high CompLit Trader can cut base prices by 40%.
The spot

The nanos and the prices

Attention !
Based on Bitnykk's observations:
- Weird "Cut Red Tape" is SOLD and uploads "Improved Cut Red Tape"
- Simple "Cut Red Tape" and Improved "Red Tape" are NOT sold