so, basically i havent found any info about that on internet, BUT, after trying and logically thinking, i came up that its actually really easy.
1. in the room with npc u need to look at the map behing the npc https://imgur.com/rRmuSco.
U can see that different cities have different colours, thats important.
2. now depends on what city is the closest to the needed tower, that colour u need, so for me its purple.
3. and to find the driver i just had to travel to other city that is labeled the same colour as the map, for me its Wolkin (i got lucky and for me its the first one) and look for the driver https://imgur.com/a/OmlZWe7

i saw someone didnt saw the house under the bridge, or something like that, so ig look better, if u still cant find it try to abandon ur quest, and then accepting it again