Why won't any body answer this question. Are you all too busy doing market research for Lee!
With your finger ends in the fret (speaker cover) material, pull the sides of the fret frame outwards and towards you. The fret should then just lift away.
I am not sure that you can order replacements from B&O any longer. Check with your B&O dealer, he may be sitting on some stock.
They are usually available on eBay but I confess to not noticing any lately.