Need Specific Vitamin Suppliments

I'm interested in finding a vitamin shop other than GNC (too expensive) where I can buy selenium, glutamine and l-tryptophan. I can find the selenium, but I'm having problems finding the amino acids.

I've been to Super Cheap, Tesco - Lotus, Big C, Central, etc. I'm looking for a place that would either have these items or could order them.

Thanks!