Where are the Dads of Donor Insemination Conceived Kids?

I am beginning to wonder where are the other dads like me? They must exist. I am curious how to find them. Do they wonder the same thoughts as me? Do they wrangle with thoughts of the donor? Why aren't they looking for others as well? Are they internalizing their thoughts? Are they reading books and do they have comments on them?

Here in the USA there appear to be few groups that address the social fathers of donor insemination conceived kids. I need to explore the UK Donor Conception Network site more to see what percentage of active members are the fathers. The same goes for the Australian Donor Support Group.

Is it perhaps the stigma that a donor was needed to create their children that keeps them from speaking up? I wonder.