How to revert back to stock rom for Galaxy S 2? Possible Duplicate:
  Where can I find stock or custom ROMs for my Android device?  




I did the whole exercise and rooted my Swiss Sunrise 2.3.4 Galaxy S II ending up installing CM9 and the ICS 4.0.3 preview without TouchWiz shown and described here:

http://devsrom4android.blogspot.com/2012/02/samsung-galaxy-s-ii-android-ice-cream.html

I do not have a backup of the original stock rom from Sunrise for Switzerland and with this new version I cannot install home banking application (it's restricted for swiss devices and for OS version) neither can I install the new Chrome Beta for ICS because it tells me country is wrong.

where can I find a step-by-step guide on where/how to find the original rom and put it back possibly also unrooting so to bring the phone to its original state/configuration? Thanks!!
You can find the stock ROM for the SGS2 on XDA here, and there is also a list of branded carrier ROMs here.

You will then need to use a tool like ODIN (maybe even Kies) to flash the ROM to the device. The first link also is a good tutorial on how to flash via ODIN. 

I recommend you read everything before you attempt to restore, then when you understand it all, read it again. If there is any reference to specific versions of things, or radios versions or anything like that, make sure you do the research and look in to that stuff and make sure everything is "correct" before you continue. Then follow it step-by-step when you are ready to restore.