300 f/4 AF-S lens tripod collar

My tripod collar, that goes round the near end of the lens, has broken and I need a replacement. I don't want the Kirk or RRS ones - they have Arca Swiss bases and I use a Manfrotto 701HDV tripod head, which uses a different type of qr plate. I can't find the collar for sale at any of the usual camera stores. Does anybody know where I can get one?

Thanks,
--
Richard (rb_stern),
http://www.pbase.com/rb_stern
richard-s.smugmug.com