I know scant details of him, but this is what I do know: Lived in an apartment building called Top Hat in Long Beach, CA in 1976 (this does not exist anymore); had long blonde hair w/blue eyes; was (I believe) married to someone (not my Mom); his first name is Brent.

I'm sorry, but that would take personal sleuthing that you can only do by knocking on doors around that area, and even that is a one in a million. I'd say nursing homes, but he could easily be about 60 now, too young. A first name of a married man is just not enough. Usually starting with your own family is the best option. You could put an ad in a Long Beach newspaper. But these days people move a lot... how many family members do you have?