Salam leaf (syzygium polyanthum) - aromatic leaves used in Indonesian cooking similar in use to the bay leaf. Bay leaves are not a good substitute so try curry leaves which can be found in Indian grocery stores. Although it is referred to sometimes as Indian Bay Leaf it is not the same thing. Fresh salam leaves are best if picked and left off the tree and allowed to shrivel for a few days which helps to draw out the essential oils.
Given the difficulty in finding fresh leaves you can source dried leaves in Indonesian specialty shops and there are several sources for them online. It is important to make sure to fry them in a little oil to help bring out the flavor.