Try this old but interesting looking, dice dare:
https://www.getdare.com/bbs/showthread.php?t=253273
It says at some point to find "motiviational material" by googling for specifically themed tumblrs. But I guess these days, that isn't working well anymore. So maybe look for specific NSFW subreddits or just go on a porn streaming site that offers category filters. Anyway, hope you have fun.