Proximity gadget / switch

Dear madam / sir,

I am looking for a simple gadget (to build or ready made) which allows me to detect a person passing by, at a distance of approx 0,5 to 2 meters and which is able to swith 220 volt AC supply (or alternatively 9 volts DC).
I am looking for a relatively small size detector (e.g. max. 1 or 2 cm wide) which can activate some led’s for as long as a person still stands in front of the piece of art at a distance of say 0,5 to 2 meters.

I would be pleased if someone can advise me how to realise the above.