The VIA documents mentions using a "2600mAH power bank". These provide a regulated 5V output from a USB connector and can be charged from a phone charger with microUSB plug. Ebay had them for 99 pence (shipped) so a couple were bought.
Testing them to power the VIA externally proved they would work fine. The BIG issue was that power bank box was too big to squeeze into the VIA so the power bank contents would have to be extracted from the package. This was done but it was quickly discovered the controller boards are destroyed if 5V from a charger is applied without the battery connected. The LIPO cell still worked. Time to look for a more robust charger for my growing LIPO cell collection
Adafruit had a Powerboost 500 charger/booster which looked to be well suited. It also had the advantage that the VIA could be powered at the same time as the cell was being charged. One was obtained for $15 and squeezed into VIA with the LIPO cell, as shown below.
|Controller shown top Left, just above the LIPO cylindrical cell