You may be able to use jsadebugd (JDK) to attach a debug server to the process (available on Windows with the Debugging Tools for Windows). It is marked as experimental, so you may want to try it out on a test machine first.
Usage:
jsadebugd <pid>
jdb -connect sun.jvm.hotspot.jdi.SADebugServerAttachingConnector:debugServerName=localhost
The connector name withe arg can be found using jdb -listconnectors.