I just found a bottle of Helmut Lang Eau de Cologne. I had been wanting to get a bottle of it forever so I was thrilled to snap up the one bottle I saw.
I don't know what would be comparable to Helmut Lang EDC besides the "women's" Helmut Lang-- the Eau de Parfum. I actually have the EDP also of the Helmut Lang, and it's very similar to the "men's". Maybe even a bit better. The mens' starts off nice, but quickly gets a "dusty" character about it. The womens' starts off the same but stays creamier and retains its "baby oil" quality for longer. It's a bit smoother. So if you scan the internet and see a bottle of the Helmut Lang Eau de Parfum, you should try it. Very similar.
As to what other fragrances smell like Helmut Lang Eau de Cologne, I have no idea. It is pretty unique when you think about it. A fragrance that isn't all that similar, yet has the same effect on me is Tam Dao by Diptyque. It's a simple creamy sandalwood with a bit of musk. When Helmut Lang dries down on me, it smells a little like sandalwood incense. So I'm making the recommendation of Tam Dao as something you might enjoy. I remember the day I got my Tam Dao I was completely blown away by how perfect it was in its simplicity. I always get compliments on it as well.
Don't give up hope on the Helmut Lang-- there are bottles floating around out there, you'll get your hands on one soon enough if you keep looking.