The sign is already there, 
https://twitter.com/cmorenville/status/1316799901691531265
https://www.vrt.be/vrtnws/nl/2020/10/15/oprichters-brailleliga-geven-hun-naam-aan-plein-in-sint-gillis/

If you add the square can you notify me so I can create a wikidata for it (if you want you can do that every time you add a new street)
Élisa Michiels: Q116864463
Lambertine Bonjean: Q116864436