Where can I buy an international calling card online to call the UK that is under $5

All the cards I am finding have a $10 or $25 minimum and I only need it for one call so a $3-5 card is good enough. It also needs an instant PIN so I can make the call today.

http://www.callingcards.com/shopping/rate_table1.asp?AffId=3020&link_id=7&Origin=USA&Destination=USA&GUID=BC4DA020060C604E886E0E826B5906FD