A forum member's elastic Irvin collar securing strap is currently selling for £122! They usually sell for about a third of this price. I have paid less than this for an entire original Irvin!
http://cgi.ebay.co.uk/Rare-WW2-RAF-Irvi ... 0206447493
http://cgi.ebay.co.uk/Rare-WW2-RAF-Irvi ... 0206447493