I'm guessing the reason you don't see any information because informal post-baccs are very subjective and a broad term an can virtually be done anywhere. You can enroll at any 4 year university as a quick entry student or a part time/full time student and take any classes that you feel that you wish to take. You can also enroll at a CC and it would be an informal post-bacc as well.
The reason you hear discussion about formal programs is that they have a structured curriculum that is largely not subject to much change and grant a certificate/degree at its completion. It probably has requirements such as a minimum GPA maintained in the program as well as X number of credits and such and go through an applicatoin process with such and such admissions requirements. Informal post-baccs normally have none of that and are purely subject to whatever one wishes to take/do.
