I was browsing a new (to me) raw food storefront, Vivapura, and came across their "sweetener of choice" -- Jerusalem artichoke syrup. They claim it's the lowest-glycemic raw sweetener available (well, besides stevia, I suppose) with a GI of 6. They stopped carrying yacon syrup because they liked this one so much.
I have been trying to find this as well. Cafe Gratitude sent an email about it a while ago, but I have yet to find it as well and I don't know anyone who's tried it. I love yacon syrup and coconut nectar, but this would be a great third option for unbaking.