Connecting PCB to Bus bars and assembly
Do you know any assembly company that would support placing bus bars on the PCB?

I think most companies will do special requests, they may charge extra. If your thinking of soldering the bus bars to the PCB then if its relativity manufacurable then some will, if its not then they may say &quot;we aren't comfortable doing this process&quot;.

Maybe there is any alternative solution instead of bus bars? Are you
aware of any other, like specialized power PCB with local thicker
copper? Of course - looking for low cost of service.

There are companies that I've seen that do thick copper (3oz or greater). There are also some that integrate bus bars into PCB's these come with associated costs. But if you want to keep the copper within a 60C rise above ambient with 200Z you'd need a trace that is 5oz and 2&quot; wide at least.
A 3oz trace would need to be 3&quot; wide.
Another thing is this will be a challenge to solder, as during assembly the PCB will struggle to warm up to the temperature to melt solder.

How about screwing up bus bars to PCB instead of soldering? Would it
work properly?

It should, as a designer, calculate and keep the resistance low. If you need to use multiple fasteners parallel them to keep the resistance low.