Go to a drywall supplier. You should be able to find one in your area by using the yellow pages. 1/4 inch drywall is pretty much only used for cosmetic repairs, so most DIY stores don't carry it. If they did, people would use it and then wonder why the wall caved in when they bumped up against it.

We get them from a local building supplier--NOT a big box home center. The cost is about $4.50 per 4'X8' 1/4" sheet--delivered at no extra cost.

Another possible source is a mobile home supplier. I would try them as a last resort, for they are probably more expensive.

David

I like to use 1/2 for samples.

1/4 is also used for radius applications.

I keep my boards behind my seat in my work van, holds about 15 samples. I dont do all my samples on 1/2 ", but I took what I could get at times.
I prefer 1/2 or even thicker for samples, but yes they are a bit heavy. My thicker samples are only 6x6 sometimes.
I dont have time to drive around and hunt down 1/4" boards.
I grab what I got.