Good day everyone,
I stumbled across this forum looking not specifically related to Asperger's or autism, but more generally natural ways to release oxytocin. As for deficiencies (a real lack of oxytocin levels), I'm not sure what can be done, but I am aware of mental visualization exercises (read: imagination) that can *release* oxytocin that's already present.
Strong, vivid visualizations of hugging a family member, or other unmentionable activities with a spouse or significant other can release oxytocin on demand. An important note, however: you should make sure that genuine love for the person is present and not clouded by any negative feelings such as anger or frustration, as these will release completely different, unhealthy chemicals. Also important is that word "love" here, as I do not mean "lust."
Short of a deficiency of medical nature (if there is one in either Asperger's or autism then I apologize), oxytocin is found naturally and only needs to be released. Sleep and good nutrition should be plenty in normal circumstances to rebuild the supply on a daily basis.
I am an avid reader of neuroscience books, which is how I came to gather all of this knowledge, and you can find a good book called "Your Brain at Work", which has a good primer for neurochemicals, even though the information is presented in a practical business-oriented text.
Cheers!