Portable vocal booths

I'm sure you could build your own, but as far as I've seen through a bit of research on the subject, if you buy a cheaper one or make your own, it's not going to do as much for you as you really want.

It's lame that this kinda stuff is so expensive, but there's science to it.
Try doing some research and building one yourself. I think you can make one with cheap materials you can get from your local home depot/music store.
 
I got a basic filter with my nt1a years ago. It's just foam without the plastic backing that other ones have. It really works! no reflections.