[Arran]

A Hammond, or any other North American made isolation transformer would be fine, and cheaper if they are second hand. I have at least one isolation transformer someplace but have never used it, most of the radios I work on are AC sets, which are already isolated from the power line, unless they have a leaky line capacitor going from the hot side of the line to chassis. In the case of AC/DC sets most of the ones I have are not hot chassis sets, and I really have no reason to work on them whilst they are plugged in unless I am aligning them or performing a voltage check.
Even with the AC sets I usually do most of the work whilst the set is unplugged, most of the checks can be performed with an ohm meter if there are doubts, paper and electrolytic caps always get changed, unless they are obviously new.
Regards
Arran