Zero999's circuit is roughly what I wanted to suggest.
With the Q4/Q2 totem pole, I think it might even be feasible to increase R2 and R3 10x to reduce power dissipation on Q3 which is currently 1W at 100V.
If V2 is 5V, what are the collector and emitter voltages on Q3?
That's a standard BJT current source. B-E junction is basically a diode, so driving the base at 5V pulls the emitter up to about 4.3V. Then there is ~11mA current through R2. Due to the current gain of the BJT, only a small bit actually comes from the base and majority from the collector. Collector voltage dynamically adjusts to maintain that 11mA, here it will be 11V below the top rail.