Sounds like you found a solution? That cable from Amazon will only work if the outlet is a 240/120 V combined outlet, which includes the neutral and ground (4 prongs), allowing you to tap into one of the two split phases. In other words it would have to be a NEMA 14 series or 14L series twist lock receptacle. Had it been a NEMA 6 series 240 V, it would not include the neutral and a cable splitter like the one from Amazon would not work.
Another more expensive option is to get a portable EVSE adaptor like the one from SPX, which comes with a 240 V plug, and should be able to charge the Volt at a higher rate, adjustable on the adapter itself.