Just sharing the 3mf file from this, so it's easily printable. https://www.printables.com/en/model/151437-handle-insert-for-clothes-basket-design-example

I found I needed a couple of raft layers on a P1P for proper adhesion. The original has pins and suggests gluing. I didn't bother with that, as it fits snuggly in my basket without gluing. My basket is Sterilite, marked 1217N3. Looks like this one: https://www.sterilite.com/product-page.html?product=12178006