I would give them to Aisha at DARC. You can email her [email protected].
K9 used to take boxes like that and sell them to raise money for their dogs, however they are not so easy to get hold of (k9 friends I mean, they hardly ever answer the phone)
We have a large wooden travel box for a dog which ours travelled out from the UK in - we had a black labrador.
It's free to a good home and I was wondering whether K9 or one of the other dog adoption groups would like it. It's wooden with a mesh door. Can email photos if anyone is interested.