"SWID was released today in the UK... I was in London and the Piccadilly Circus HMV store had plenty of copies (I saw about 30 copies scattered around the store). Cheap too, at £1.99."
And for the US, "Friend of COF" says that FYE should have the single in stores tomorrow. Best Buy, Borders, Newbury Comics and Virgin also bought copies, but is not 100% sure if they will have them tomorrow. So check with FYE first.
(Thanks Friend of COF)
Updates: "For anyone in Virginia, the record store Plan 9 got copies in today. " (Thanks believer-ko)
"Earshot in Greenville, SC has it!!!" (Thanks Caterpillargirl2)
"Singles available in Southern California @ Mad Platter (Riverside) and Rhino Records (Montclair, or is it Clairmont). Sorry, but no 7" Vinyl singles." (Thanks Haloburn)