Can someone please recommend books for my toddler that simply address separation anxiety in the plot?

My son is having the normal sleep anxiety issues before he goes to sleep. We already have a routine and a consistent bed time. However, I’d like to read him a book before bed/nap that addresses the issue of separation anxiety. Will someone please recommend a story book that i can read to my son. I’d like it to reinforce the basic principles that I am here for him if he needs me even if he can’t see me, or is asleep.

I haven’t read these particular books, but I went looking on Amazon and came up with a few options that look pretty good.

Mama Always Comes Home (we have some other books by Karma Wilson and they are pretty good)

http://www.amazon.com/Mama-Always-Comes-Karma-Wilson/dp/0060575050/ref=pd_cp_b_3

“You Go Away”

http://www.amazon.com/Away-Concept-Books-Albert-Whitman/dp/0807594423/ref=cm_lmf_tit_5

“Owl Babies”

http://www.amazon.com/Owl-Babies-Martin-Waddell/dp/1564029654/ref=pd_sim_b_7

Better Nights Sleep Treasure Hunt – Mumoocie