I'll add this one, representing the Belgian Army trained in Ireland during the occupation.
(The one with the cron represent the land component of the Belgian Army) :
https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.1579.be%2F40-45%2Fbrigades-irlande-2.jpg&f=1&nofb=1

Extraordinarily helpful thank you. This is enough for me to do all of Belgium.

Thank you very much ! I also propose the 5th Special Air Service, an exiled of mostly Belgian soldiers : https://en.wikipedia.org/wiki/5th_Special_Air_Service

Two possibles insignias :
https://upload.wikimedia.org/wikipedia/commons/e/e9/1PARA.jpg

https://upload.wikimedia.org/wikipedia/en/f/fa/SASWings.png

It's me again, this quarantine give me too much free time. é_é'' So I thought about adding some other coat of arms and flags that could be used, just as a ressource. It comes from the three regions of Belgium (Flanders, Wallonia, Brussel) and from its, back then, 9 provinces :

Insignia for the city of Brussel :
https://en.wikipedia.org/wiki/City_of_Brussels#/media/File:Insigne_Bruxellarum_coronatum.svg

For Flanders :
https://commons.wikimedia.org/wiki/File:Arms_of_Flanders.svg?uselang=fr

For Wallonia : https://upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Coat_of_arms_of_Wallonia_%28Belgium%29.svg/800px-Coat_of_arms_of_Wallonia_%28Belgium%29.svg.png

For the provinces, you can see the arms of each provinces here (along with the flags) :
https://en.wikipedia.org/wiki/Provinces_of_Belgium

Now, there's also some well known rexist collaborationists insignias used by para-military organisations and the SS divisions from Belgium.

Flag of the Flemish Legion :
https://fr.wikipedia.org/wiki/27e_SS-Freiwilligen-Grenadier-Division_Langemarck#/media/Fichier:Flag_of_the_Flemish_Volunteer_Legion_(Legion_Flandern_SS).svg

27e SS Division Langemarck (Flemish SS)
https://upload.wikimedia.org/wikipedia/commons/5/5b/27divss.gif

Insignia of the Walloon Legion :
https://en.wikipedia.org/wiki/Walloon_Legion#/media/File:Wallonie_shield.svg

28. SS-Freiwilligen-Panzergrenadier-Division « Wallonien » (Walloon SS) :
https://fr.wikipedia.org/wiki/28._SS-Freiwilligen-Panzergrenadier-Division_Wallonien#/media/Fichier:28._SS-Freiwilligen-Grenadier-Division,_%E2%80%9EWallonien%E2%80%9D.svg

Flag of the same division (the cross of Burgundy was widely used by the facists in Wallonia) :
https://upload.wikimedia.org/wikipedia/commons/b/bd/Wallonische_Legion_Version_1.jpg

https://fr.wikipedia.org/wiki/28._SS-Freiwilligen-Panzergrenadier-Division_Wallonien#/media/Fichier:Wallonische_Legion_Kompaniefahne.jpg


Also, on a lighter tone, for the airforce :

Belgian Air Force roundel :
https://upload.wikimedia.org/wikipedia/commons/0/07/Roundel_of_Belgium.svg

Aviator badge of the Belgian Airforce :
https://upload.wikimedia.org/wikipedia/commons/5/56/Aile_COA-3-coul-20x7-300dpi.jpg