Hi J,
welcome at Stridaforum 
Did you try here?
https://www.velorution.com/
Back then sold Strida France some of the ancient parts but I’m afraid there isn’t anything left over.
You need to ask them yourselves:
http://strida.fr/
There is still an official source for that part; unfortunately not in Europe, but in Korea:
http://koreamtb.co.kr/shop/item.php?it_id=1503020790
I’m definitely not sure if the brake assembly is all you need for flawless function.
But I do have a few of these brake assemblies laying around here in Vienna 
Maybe you want to mail me? 
Cheers,
Chris