Does it have to be an actual SIM card?
Some text and call applications give a number that stays the same if used periodically, so you might get by with just data access and no need for an extra phone.
Or did you lose patience with the various providers on your previous thread?
http://www.prepaidgsm.net/forum/showthread.php?t=8347
Note that although the FreedomPop roaming SIM you mentioned there seems to be no longer available (well the former UK supplied one anyway) it is possible to use the service even without a SIM - just install the app and sign up.