power supply can be definitely mad and i have few schematics that are designed good and reputed firms.
as a designer, O P might know it is non-isolated and he can be careful also.
even he can caution other friends for whom he makes to be careful.
but how about children and uninformed about the perils of shock that might bring life risk.
Life in general is NOT CHEAP?
i join the other members, surely advocating against non-isolated PSUs.
there are many, cell chargers with 50/60Hz transformer-less, but following that DC, it is converted to isolated DC by a ferrite transformer of cute size, thus it gains the reduction of mains transformer, at the same time giving isolation by SMPS mode miniature transformer.
finally such design can deliver around 500mA at 5V
the overall weight would be less. it would not be too costly if made in bulk.