i'm able to find eeboo games at a local teacher's supply store. do you have something like that near you or an independent toy store?
since you only have a day and toys r us may be your only option, perhaps you could just go with the toy story idea (since you know it's something she likes). i think the coloring book and crayons (or colored pencils) that someone mentioned is a good idea. i also found this and this and this. and all for $10 and under.
or you could go with the horse theme. i liked the stamp idea someone had. this combines both.
or what about memory? dd loves hers. there's even a toy story version.
dd also loves this game.
i'd have many more suggestions, but i'm looking for things you can find at toys r us.
what about a set of card games? dd got go fish and old maid (the eeboo ones, which are really nice) for x-mas and she loves them.
this is another fun game.
good luck! i'm sure she'll love whatever you end up getting.