Yelpers seem to like the Custard Pineapple Buns aka Pineapple Puffs 2 for $1.50 Cash Only at Pineapple King Bakery, SF. Might have to ask for them if you don't see them. They also sell cocktail buns & egg tarts. Who's tried them?
Pineapple King Bakery
1915 Irving St, SF (b/t 20th and 21st Ave)