Relax.... beanbags can be found! I have 2 and I have them from Dome. They can make them in a lot of colours, not cheap though. Mine were about 22 usd per piece and thas was a while ago.
For colourful ones, try the furniture shop in the Vincom towers, sorry, forgot the name. Recently I saw beanbags there as well.
If you want cheaper ones, try Can's rattan. They don't have them ready made, but will make them to order.
As far as appliances go: I would try Metro, was there a few days ago and they have expanded their appliances section.
Almost opposite the Metro is a large appliances store as well, but that is geared more to washers, dryers, TV's, DVD players and the like. But it might be worth to have a look there, as I remember that they did have a kitchen appliances section as well, it's just that at that time I was out to buy a TV only.
You have to have a Metro card to go and shop there, do you have access to one?
It's probably not helpful, but four years ago I bought a beanbag chair in the northern part of the Old Quarter, on a the street where they sell blankets and small beds and pillows. It cost about VND100k and it lasted about two weeks at my house before my dog peed on it and we had to put it out on the street.
I'll drive by the street tomorrow and see if the store still exists.
