The Olympus eSif lists the slide-on hood for the 55/1.2 as US part# 108-233, while the hood for the 50/1.4 (and 50/1.8, 35/2.8, etc.) is part# 108-230. The difference is that the 108-233 can be reversed for storage on the 50/1.2. I would guess that the 108-230 is just a tiny bit smaller in diameter, making reversal storage very difficult if not impossible. In fact, I find the 108-230 difficult to store on my late production 50/1.8 miJ. My s&le of 50/1.8 miJ is ever so slightly larger in diameter than my other 50/1.8s and my 50/1.4. The difference seems to be in the focusing ring rubber.
Well, that's a VERY good question. It's going to be fairly difficult. oBoy is an obvious possibility, but I would also check KEH and other sellers/shops with an online presence. If you belong to the Olympus list (http://zuikoholic.com/) you can post a wanted to buy there.
> The 55 1.2 and 50 1.2 are two very different lenses. The 55 is the older, single coated and takes 55mm filters, the 50 is multicoated and takes hood 108233 and 49mm filter. John, http://www.zuiko.com