Plastic insert damaged when tried to open gravity wheelguard ixow Can anyone tell me where I can find to buy the plastic insert from the wheelguard?
For completeness - this is a part custom to your brand and model of frame.  It doesn't seem to be related to your choice of wheel skewer.

So your best option is to contact the manufacturer of your frame directly, or their authorised agents in your area.

Based on the linked question, you have a Canyon Commuter, and their contact information for you is based in Koblenz, Germany.  https://www.canyon.com/en-ro/contact/  You can use telephone, live chat, or email.