Looking for a step down converter for my HAL Handy Scanner I found this:
Step-down Converter 230 -> 110v 50w

Quite affordable (lowest price in the Netherlands, Euro 9,95) and in a nice package.
Also convenient and powerfull enough for most MSX2+ and turboR machines imported from Japan.

It is cheap and cheerful! The one I use for my TurboR cost my £15 (fifteen UK pounds!) it works well without any problems.