UPDATE: The reported issue with the bridge has been solved. Additionally, you can now downland both right to left and left-to right orientations of the bridge.
This collection of GraviTrax Junior-compatible tiles contains replacements for all basic tiles. I have also created and remixed a few decorations to make them GraviTrax Junior-compatible decorations (capybara, elephant, and owl) that I had to publish separately and split due to a conflict of licenses. If you want to extend your marble run by an additional piece, you might look at my GraviTrax Junior compatible tunnel.
All parts can be printed without support and assembled without glue.
I printed all the pieces in PLA in my testing, but other materials should also work.
Except for the foundation and bridge parts, all models are Remixes.
The author remixed this model.
All remixed models were adjusted and improved so that a) you can print them without support and b) you can assemble them without glue.