The diameter is 10.5 cm. There is a branch of Emerio in Switzerland, they have spare parts. I have also needed spare parts and they even delivered them to me free of charge. The best way to enquire is to send an email to info@emerio.ch - more information at https://emerio.eu/verkoop-ka....

You can measure it on the basis of the scoops and then take any substitute, such as a biscuit cutter, a glass, a mug, etc.