Dabs.com, Scan.co.uk I hear also supposed to carry them. All prices Ive seen so far are around the £50 mark for the 128mb version.
Beware with 7dayshop, they take a long time to complete your order. About 10 days it will take from online order to delivery. Pretty poor in this day and age. I won't have my SD card before I have to decide if I am to send my SPV back!! They are in Guernsey which is why it takes so long.