This is a replacement lid seal for a Starbucks - "Been There Series", Across the Globe Collection, 16oz:473ml mug.
I had no luck finding one so I decided to model one up and make it out of TPU. Works fine and no leaks so far.
I used 95A TPU which is fairly stiff compared to silicone. Take your time installing it, so you don't break the small retaining tabs on the lid. Maybe warm it up a little before putting it in place.
The author marked this model as their own original creation.