Great question!
I'd vote for the car or some quiet spot in the workplace with a sign on it, for 30 minute naps, 90 may be harder.
I'd vote against the toilet stall
I have been surprised at how many people I've just chatted with abt this whole thing have come up with positive responses. I work in the health care profession so can usually actually find something close to a bed (yah, eatcherartsout but there's ups and downs to everything

)
At the same time, I wonder whether in more working situations than expected, some trade arrangement might not be possible. This takes creativity anyway doesn't it? So maybe batch up the off time for that and trade offices? or something