SO many options!
I will share what we use and love.. it's called the Sleep Sheep! It's actually a sheep stuffed animal that doubles as a white noise machine too.. the buttons and volume are on the back :) It's soooooo cute, it has a velcro strap that you can hang on things as well.. ie.. we hang the Sleep Sheep on the outside of Monroe's travel crib, so it isn't in the crib with him.. now it also has a cool feature in that you can select the time options, choosing from 23 minutes or 46 minutes that you want it to play.. and I know, weird number choices :) ha! The sounds are great, we use the "ocean" one.. and we just honestly love it! It can travel anywhere and love that it's plush like a stuffed animal too!