May I suggest something like this:
Wellgo V12 Copy Flat Pedals | Chain Reaction Cycles
They are a flat mountainbike pedal, designed for a flat "downhill" type flat soled shoe as opposed to the clip in type which have a similar system to a ski clip.
I think a flat MTB pedal will spread the load on the soles of conventional shoes and avoid the cutting in to the sole you have experienced.
Cheaper versions (with cruder bearings) are also available.
PS: The left hand pedal has a left hand thread. ie It screws OUT clockwise.
I hope this helps.