I see them in store fronts, at the temples in random places all over but where the heck do I go to buy one for my house?
there is many kinds of lanterns, would you please specify?
Maybe a screenshot can help.
Modern lanterns are mostly made of plastic which is not for decoration, only for kids showing in the festival.
Here is some lanterns for decoration you might want to take a look.
This is the biggest auction site in taiwan, it almost have everything you want to buy.