Is there a medical link between aspergers and cerebral palsy? And what treatments are available to an individual who is living with both?

Relationships. I know of no causal relationship between CP and asbergers syndrome. However, in both instances therapy should consist of physical and occupation therapy. Speech therapy is also very important. Art, music and play therapy should be exploited.
Not to punt but. You are gonna need the advise of good local doctors. Your pediatrician could place the child into physical rehab to get improvement; a child psychologist and psychiatrist will be instrumental. I have seen no link between the two but not an expert. Good luck, u will find a better answer.
Comorbidities yes. I do not know the rate of incidence of this but i gather that there are people who have the added diagnosis aspergers who have cerebral palsy and the reverse, a certain rate of disease of cerebral palsy patients with aspergers. The treatments for behavioral modification may be conicidentally the same therapy. But each addresses the the functional problems that each conditions shows.
No. Although these conditions can co-exist, there is no common cause or physiology involved. Clearly, it's a much bigger burden to have both conditions, but each condition can be improved, and should be aggressively treated. These more complex developmental cases are often where a good behavioral & developmental specialist can be especially helpful.