Where a 110v mains is not available on sidewhat device is commonlyused to provide the required reduced low voltage?

In Europe, where the voltage is 230 v (nominally), hand tools used on building sites commonly use a 110 v centre-tap supply for safety, with the centre-tap earthed so the maximum voltage to earth is 55 v.

Portable Transformers with two 16-amp output sockets are often used and they can be found for about £30.