Using a current mirroring source to power 6 Nixie-Tubes
Okay, so you want to dynamically adjust the 190V converter down to 120V after switching. 

You don't really need closely matched transistors for this application because you have relatively (and appropriately) large emitter ballast resistors. You can use MPSA92 transistors which are cheap and very widely available. 

For example, suppose one transistor has a Vbe of 0.6V and the other has a Vbe of 0.65V (because it's not as hot, say) then the difference will only be 0.05/3V which is less than 2%. Temperature variation will probably be more important than unit-to-unit variation but I doubt it's a problem for visual brightness. You could minimize it by putting the pairs together face-to-face but again I doubt it's worth it. There is also an SMT version available MMBT.. and mounting them close to each other doesn't hurt. 

You can use MPSA42 NPN transistors to drive the current mirrors. Again, cheap and widely available. 30mW (check your numbers) is not very much dissipation at all. Below 200mW for TO-92 or about 120mW for SOT-23 you're likely fine in any reasonable environment. 

The 'rating' of 625mW on the TO-92 transistors is a bit of an exaggeration but 1/3 of that is not unreasonable. Note that if the output somehow gets shorted the transistors will see 560mW with the 190V supply, which will make them very hot fairly quickly, but should not kill them instantly if TO-92.