Bought a cable from here:
http://www.ebay.co.uk/itm/271854384572?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I was a bit concerned that it would be OK as it seemed cheaper than elsewhere, but my Sonic Port VX arrived today and no problems with it whatsoever.
I had also checked with Line 6 that the VX would work with the Ipad 2 as it was not on their list of approved devices (or on the list for the Sonic Port even though it does come with a 30 pin connector!) They confirmed that the VX will work with the iPad 2 - and it does.