Someone I know weighed 40kg and was terribly under weight (ribs sticking out, cheek bones very sharp, etc) and started taking alfafa tablets recently that seemed to help a lot. She's put on some meat on her bones and is looking much better! Just thought I'd share..!

Ummm I guess they must have it at pharmacies? Have a look around?
From my own personal experience, taking spirulina/chlorella too can help with weight gain.. You just have to find the right blend and brand that suites you best.. =)