We lost our boxer bitch earlier this year to cancer, we are now ready for a new bitch preferbley red and between 5 to 12 months old, that has been brought up with other dogs.
Thanks

Why don't you contact your local Boxer breed rescues?
They may have some youngesters that are looking for homes.

Also worth trying your local rescue centre, as they sometimes have pedigree dogs that need rehoming.
You could also check out a few boxer breeders as they sometimes have slightly older dogs that they want to rehome.