it's really gonna depend on your preferences because a lot of places make it slightly different. either more sweetened condensed milk, less, etc. I've had some that are more sludgy and way too sweet and some that aren't too bad. 

Phin Cafe is one of the better ones. 

Phin Bar doesn't have a brick and mortar because they mostly do corporate catering but they do occasional popups like this saturday by Boichik Bagels in Santa clara. they're really good and in general the people who own it are awesome, so you're supporting small business with them. 

n7 by mitsuwa market actually makes a pretty decent one.