An interesting and cheap way to see these places would be to rent a bicycle. Next option would be to work out a deal with a cyclo driver
Renting a bicycle seems like a fantastic option to explore the city and visit those places if you can work your way out of the hectic traffic in Hanoi and can navigate really well.
Another way is using Grab application (just like Uber) to book a motorbike and try out a new experience on bike riding. It is like a motorbike taxi, you don't have to bargain and you can choose your destinations beforehand with an estimated fare.