I have a stock of cardstock cut to size for boarding passes for sale (I've switched my cutter and can't use these any more). They are pre-cut to 3-1/4 x 8-1/4 inches, in premium bright white matte cardstock (100#). These can save you quite a bit of time and effort in cutting if you are making DIY boarding passes.
I will sell in batches of 50 sheets for $3.00 plus shipping.
PM me if you are interested.