im thinking of getting some of this:

L Leucine from Myprotein

for the amount you get it should last ages.

ive read a fair amount about leucine and it seems that between 0.05-0.06 per kg of bodyweight maximises protein muscle synthesis and its leucine that is largely responsible for protein synthesis (obviously not the only factor)

Leucine regulates translation initiation of protei... [J Nutr. 2006] - PubMed result

Orally administered leucine stimulates protein syn... [J Nutr. 2000] - PubMed result

Leucine - Wikipedia, the free encyclopedia

T NATION | Supplement Research Update: Leucine and Protein Synthesis