How about the old EF 24mm f/2.8? It's small, decently sharp, and reasonably priced. However, it doesn't have usm, so it's got noisy AF and it's built like the 50 1.8.
It's built like the 50 1.8? Do you own this lens? I did once, and its build is better than the 50 1.8.
I recommend the 24Lii, I have it and it is just awesome. They
say the 24L is the wide 85L.