=> I agree that there is a risk of using any adapter that does not carry the IEC 60101 rating for human safety. It is illegal to sell any other adapter for use in a device that treats the human body in the US as well as many other countries.
I has been involved in many electrical approvals under UL/CSA/CE in the 80’s an 90’s
The general rules where at that time that EVERY component involved had to meet the standard suited for the use intended, AND (this was a must too) that THE WHOLE PRODUCT, as an assembly, had to be verified/approved for this use too.
This translates, in our case, that not only the transformer, but the whole transformer+zapper+accessories had to be approved.
This is a tedious, time consuming, very expensive project approval most manufactures try to avoid, when possible. This leads too, for some manufacturers to “cheat” and/or transfer the responsibility to the final customer, unaware of this "transfer", a very bad practice.
For these reasons, I feel that even if the transformer is approved IEC 60101, the whole unit poses a safety and legal problem, most of the time.
As long as electrical safety rules applies (with the line involved), 9V-batteries-only are the only way to go.
If anyone knows what are the actual rules, please, lets us know. (I'm expecting more rules, not more simplicity.)