Hi Jamey,
i've ordered one at rockauto in the us
http://www.RockAuto.com
they are 36,53 dollar including shipping to Holland
you could even consider ordering 2 just in case, i did and was happy as 1 doesn't work properly, for the two my total costs where 50,10 dollar which comes at 29 pounds
which is waywayway cheaper then anywhere else, i got their adress from a bloke on Seloc who had ordered there before
the model you'll need is: STANT 10501
it's just a standard black plastic cap on which you can glue the aluminium casing of your original one and does the job as a number of seloc members are allready using one