How to create a custom Spring PropertySource that depends on a Spring Bean

I'm attempting to use the spring-cloud stack for a project that would use Zuul. In my organization we have a custom configuration stack that is xml-based and does property composition and hierarchical overrides. Because of the way this configuration is handled, I've struggled to create a PropertySource for it.

My custom PropertySource must use my Config bean, but because the PropertySources are initialized during the bootstrapping of spring boot, the application context is not fully initialized yet and I can't get to my custom Bean that exposes our xml-based configuration system.

@ConfigurationProperties appears to be entirely biased toward .properties and .yaml files. The Config bean is initialized in an ApplicationContextInitializer. Is there a way to delay the resolution of the ConfigurationProperties within the various services so I can construct my custom property source using my Config bean after it is initialized?