I guess I don't consider 'red' to be very dark... but... you could contact any of the breeders in your area and ask if they know of any dark brindle pups. If they don't breed with brindles, they might know some who do.
Denna is a reverse brindle EM (more apricot color with a few black stripes). This is considered "undesirable" in the EM standard, from what I've read, the standard prefers brindle be mainly dark with a few light stripes. Her mom was a dark brindle and dad was fawn. Her litter was quite the mix. So even knowing the breeding parents, the pups will be a mixed bag.
Here's her pup pile - she's the red brindle on top.