Purchase your own copy here: https://www.dlsite.com/eng/work/=/product_id/RE180318.html
I've uploaded a bunch of books for this couple from this artist recently. This is the last one I could get my hands on, but there are still a bunch more
EDIT 7/4/19: Goggled Anon from /u/ has produced translations for a few of these Misaka x Shirai doujins. This one is https://pastebin.com/sFeUsecX