The dehumidifier has an overflow, but no hose. However, the dehumidifier also has a pump and a hose. I run it continuously. Whenever the tank is full, the water is automatically pumped one metre up into the drain.

No. I bought it for CHF 3 at a DIY store. There is a transparent standard hose that fits perfectly.
What bothers me is the continuous operation. It never switches off and continues to blow loudly as a fan. I solved this with a timer.