I was surprised that this wasn't on Thingiverse yet, so I designed it myself. The parts are fully compatible with the original carrera parts and are held together by the red clips.
Because the original carrera parts are quite expensive and one often needs a lot of them, this is a great way to save some money.
The weight of the parts is about 30 - 40 g, considering that an original 1/60 corner piece costs about 5€ and you can get 1kg of PLA for 15-20€, this can save you up to 4€ per corner piece. Because of the ammount of needed parts, this really adds up. The only sacrifice is the red and white stripes at the edges. These parts are only singe color.
However, with the technique of @MakeAnything shown in these videos: https://www.youtube.com/watch?v=KV2AjyowXX4&t=1s https://www.youtube.com/watch?v=D7FiT5VqLSg&t=326s I managed to get a 3 colored straight piece like shown in the picture. Let me know if you want to have files for that, but I need to say that printing like this is quite some extra work... If you want, I could also try to model colored corner pieces.
For printing, lay down the flat side on the print bed and use supports for the spaces of the red clips. 2 top and 2 bottom layers should make it sturdy enough and more would be just a waste of plastic in my opinion.