You can do it with a variac. (a variable autotransformer). Get one rated for 220V, 60hz and a current rating sufficient to charge your pack in a reasonable amount of time. Make sure that it has a fixed tap in the middle (or close to the middle) of the winding. put the 110V across the fixed tap and one end of the winding. You will get 220 across the whole winding, and variable 0 to 220v on the adjustable tap. Just don't exceed the max amps rating of the variac (easy to do when charging) on either the input or the output side or you will burn it up. You can install circuit breakers, thermostats, etc in your charger to prevent damage. Also keep in mind all the safety issues such as the fact that it is non-isolated, etc.
one example of a variac:
A variac like above is small enough to fit in a tool-box sized charger, and will charge at around 10A. Also weighs about 25lbs.
You can buy new ones easily enough but they all come from china and many are rather poorly made (my personal experience). Older USA made ones from superior electric, general radio, etc. show up on ebay all the time and are built to withstand armageddon.
I built a variac-based bad boy using a very similar unit to the one in the picture (except wound for 120V) to use as a backup charger and bench tool. It's been very handy. Another handy tip: larger used computer UPSes are dirt cheap to free and contain many useful components such as relays, breakers, fuses, fans, frequently anderson connectors, and heavy wiring that can be used in the construction of your bad boy.