I would advise getting them re-foamed. Have worked on MANY NSMs and they never sound good with new speakers. This is not a hard job to corrent.
If the speakers are gone then I would get them re-coned. Or check jukeboxparts.co.uk - see if Leon has any used ones.
NSM speakers have a very light suspension. Putting in replacements will drastically change the sound of your jukebox.
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Can get kits like this.