I bet we have the same recipie. We have been trying different cereals too. Today I actually sent Post an e-mail to ask if they still made it. I will let you know what I find out. While I was looking I found the nutritional facts, and I think I know why it is so hard to replace that taste.
-wheat bran, sugar, malted barley flour, salt, fig and prune juice concentrates. (and yes, that is the ENTIRE ingredients list).
If you can find a bran cereal that has about the right consistancy, I think you could add a little prune juice (my mom and I are going to try 1 tbls) to the water you soak the 100% Bran in. We are hoping it will give it that just right flavor.
If you have any luck with the search, or know of a bran cereal that has the right consistancy, I'd love to know!