Tryptophan

Is tryptophan avaiable in the US. I work at a GNC and a lady brought in a label for this product, from what I was aware was that this was banned by the FDA in 1988 due to a contaminated package. if so where can i get it at?
What do you think of my sleep time formula the lady gave me the bottle and made my own little night night medicine it goes like this

tryptophan
kava kava
Phenylalanine