I’ve stored my signed art prints in art portfolios which are handy, but depends on just how much protection you’re looking for.
Itoya Profolio Series 11 X 14 Inch Art Presentation Portfolio https://www.amazon.com/dp/B00ED3SUA2/ref=cm_sw_r_cp_api_i_omFpFbVH15QRT
Something like this might work - it's an art portfolio that has clear sleeves that you can put the lithographs in. Theoretically it should fit in this but there are multiple sizes that you can choose from! Plus you can take off the sticker on the front and customize the front and the binding :)