I sold my Super Nintendo in 1996 to get the cash to buy a PS1 and so it might seem an impossible task in ever finding that console again. However it had a modification which would make it stand out (or at least the power supply). My PAL SNES had a junction box fitted between the power brick and the plug and it is visually distinctive (especially to me). It was done so my Dad could confiscate half the power supply cable to stop me playing games in 1993 when I should have been revising for my exams. Every now and again I browse Ebay hoping to stumble across it (long odds I know) but in posting this thread I hope someone might have seen a SNES with just such a power supply or more likely someone in the future will search for a reason why their newly acquired SNES has an odd junction box on the PSU. So here's a few more key words that one day might help my SNES's current owner find this thread: Removable section prongs lead socket connector pin.
Or why not take the controller or the ac adapter or the video cable? This mod seems like a lot of work compared to the alternatives to make it impossible to play the console. Good luck finding it though! I've never seen it, though it sounds like you're based in Europe if its a pal system, and I've only looked at snes stuff for sale in the US.