Use a pick (the thinner the better and it's so useful for other things) if you have cloth dust cap. Just insert and pull the dust cap back into shape. Have done it with mine (people can't keep their hands off of tits).
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To answer my own question, the 3 1/2" dust cap from speakerworks fits. I replaced the caps on both speakers, as they are the decorator series with no grills.One of the dust caps on my Heresy I is damaged. I bought 3" dust caps from PE which are too small. What is the proper size to replace the dust cap, and vendor suggestion? They will look a bit odd with the faded off-white cone and black dust cap, but that's not an issue.