So, I now use a 7805 and input 1 x 200ohm resistor in front of that. So bad. so it is the cheaper way.
previously you stated that under circumstances that do not justify it you preferred "the easy way", now, you under circumstances that do not justify it you want to use "the cheaper way". I think you need another job, to do what you evidently have been tasked with can not be solved by the easy and cheap.

200 ohms in front of a 7805 will make it survive a higher input but fail on a lower input.

some user power supply marked 12V but output 9V, some 12V output 18V!
for that thers is no other solution than a switcher, look at the offerings from Power Trends (TI)

Erik