Any websites/software to upload multiple designs to Teespring/Redbubble/MBA?

To clarify, I'm looking for a site where you upload the shirt design to one website and it reuploads them to other print on demand sites like Teespring/Redbubble/Society6, etc

I know Merchinformer kinda does this but wondering about other options.

Merchinformer has one. Ive used it, but I dont really know if it works that well. Im also interesed.