How do I serialize a Java object such that it can be deserialized by pickle (Python)?

I'm using a Python service that uses pickled messages as part of its protocol. I'd like to query this service from Java, but to do so, I need to pickle my message on the client (Java). Are there any implementations of pickle that run on the JVM (ideally with minimal dependencies)?

Clarification: Modifying the server side is not an option, so while alternate serializations would be convenient, they won't solve the problem here.