Between these 3 - http://www.ebay.co.uk/itm/NEW-Sports-Running-Arm-Armband-Cover-Case-iPhone-4S-4-4G-3G-3GS-iPod-Touch-/120791853310?pt=UK_MobilePhones_MobilePhonesCasesPouches&hash=item1c1fc168fe
http://www.ebay.co.uk/itm/Running-Sports-Armband-Case-Fr-iPhone-iPod-Touch-2-3-4G-/300590410516?pt=PDA_Accessories&hash=item45fc95ab14
http://www.ebay.co.uk/itm/BLACK-ARMBAND-POUCH-IPHONE-4-4G-iPod-Touch-SPORT-/110703900138?pt=UK_Armbands&hash=item19c67775ea#ht_721wt_1185
I think I am just going to go for the cheapest one (top link)