Thanks for getting in touch with us about this. We sincerely apologize for the issues you’ve been facing with this product.
To source the window pieces from an IKEA product, we can only recommend purchasing what we currently have available. However, we would also like to let you know about BrickLink - an after-market LEGO website where you can buy specific LEGO pieces. There should be some there for sale if you just wanted to buy those without buying a whole set!
We hope this helps.
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