Did you already check ConfigSeeder (www.configseeder.com)?

ConfigSeeder can provide configuration data very similar to Spring Config Server (e.g. direct integration for example into spring/spring boot based applications). In addition, it can provide configuration data to different runtime environments - there are different 'connectors' that can:

• create files with configurable content on file systems (e.g. a script setting env variables)
• create Secrets & ConfigMaps in Kubernetes clusters
• create files in git
• ...

Disclaimer: I'm one of the ConfigSeeder developers.