I used to carry small sheets just for spore prints.
I made them by getting a sheet of white paper and a sheet of black paper, cutting them in half and laminating them in plastic so I had a single sheet that was half black and half white on both sides. The standard laminating plastic is fine.

I actually got two sheets out of this and that gave 4 half and half surfaces for spore prints.
The advantage of having the contrast is that you can place a cap at the place where the colours change and get a clear print no matter if the spores are light or dark.
Being laminated in plastic means the sheets are easy to clean and they last a long time.
Plastic also lets you lift the spores off if you want to do other things with them.

One friend used to take the spore prints on art paper. She used picture frames and put the print behind glass, matted so it didn't touch. A bit artsy-farsty for my tastes but she did sell a few of them.