Well, I have NVLD for sure, it's diagnosed, and basically a PDD-NOS, not quite full blown "Aspergers" but enough for the psych people to notice something is off. Anyway, you got the exact same problem as me, I have almost unreadable body language, and it causes problems for me. As far as I know, I can't read body language very well. But yeah, having really "odd" body language like I have makes other people I think I'm odd. Uhm, I don't know, I don't believe I read body language well, I can pick up somewhat better now after having a bit more social interaction and whatever, but still, suck at it. NVLD is weird, in that sometimes you'll just be completely dead on with your assessments of people and other times you'll be 180 degrees off in them, so you don't trust your random intuitive body language reading skills much, as they're like broken.
I don't know if Aspergers really has "specific" body language. With me, I have NVLD, which sorta gives me comorbid AS, but my neurological profile is only one type of neuro profile. IE, I didn't know there were some Aspies that were visual thinkers, for example, which I'm definitely not a visual thinker. So, for people more visual spatially oriented, they could give off different body language than someone with visual spatial deficits in their brain wiring like myself. I think as far as "Aspergers" goes the "spectrum" is much too broad. For me personally, I find my NVLD diagnosis much more useful than just being like "Yay I got Aspergers" as I know exactly where things are wrong in the brain wiring.
But yeah, I don't find having an Aspie body language guide being feasible, just due to too many variables involved. Then again, I feel the same way about NT body language, so I could just be ridiculous.
It's good and bad to hear someone else has the exact same problem with me, of not giving off enough body language for people to make good judgments.