Since you're in Europe, try the Campingaz website. They're the Swedish-based company that makes well known gas canister stoves with the blue cartridges, and they are available everywhere in Europe (at least western Europe when I traveld there a few times in late 1980s and through the 1990s). Since your needs are cooking for 5 people, you could use two of their smaller backpacking stoves. They'd work great for simply boiling water and simple cooking.

FWIW: their newer blue gas canister cartridges with the screw-thread tops, will work on most other styles of canister stoves MSR, Primus, etc). The older style clamp on stoves used a canister with no threads on top, so should be easy to distinguish in a shop.