Hendrik's Accessible Transport operates an accessible taxi service as well as having wheel-chair accessible vehicles available for hire. From the iWheeltravel blog:
Wheelchair accessible taxis: the taxi company Hendriks is specialised in disabled people transportation. I used their services twice and everything went great. Here are their phone number and email address: 0032 2 752.98.00 et info.melsbroek@hendriks.be .