Best bet would be on ebay? I've managed to get a couple of packets of spare inserts.. they do come up now and again on there.. you just gotto keep checking..
Just this second checked ebay and there's some on, the auction finishes in 2 day... are these what you're after?
http://cgi.ebay.co.uk/DRENNAN-COMBO-TIPS-FOR-CRYSTAL-WAGGLER-FLOATS_W0QQitemZ230139161928QQihZ013QQcategoryZ27416QQrdZ1QQcmdZViewItem
Hope it's ok to put this link up??