Covid Test.

City Labs costs only 46 Euro. The thing is that they are usually fully booked. But if you are lucky somebody cancels and you can get in on short notice. https://www.city-labs.be/prendre-rendez-vous/

Other than that, it's really difficult to get pre-voyage tests. I found out the Commune in Auderghem now gives this possibility (same price): https://www.auderghem.be/testing