Manual enforcement is used in the Swedish, Lisbon, Athens, Austrian motorway, French, Spanish and German low emission zones, although the Spanish LEZs are moving to camera enforcement.
Stickers are needed only for Austrian, French, Spanish and German low emission zones, and Swiss pollution emergency schemes. However, foreign vehicles are not required to get stickers for the Spanish LEZs. When LEZs start happening in the Czech Republic, these will also need a sticker - likely to be mutually recognised with the German scheme.
Check on each country, where you can get the stickers.
! Please beware, some internet sites charge you much more than the websites given on this website!