Smuggling air pressure drop

For some time now one of my Pirelli P6 tires has been losing about 0.2 bar per week. That’s not bad, but it could get unexpectedly bad… If I drive to the tyre dealer and tell him that, he will certainly laugh at me, because he probably can’t do anything but change the tires. However, I would like to, if possible, let air loss “repair”. What possibilities are there?