Kato power pack maybe? It is designed for N scale specifically, and Japanese are really fastidious designers. But I have no experience, nor I have taken any measurements.
I would also think that any power pack from a reputable manufacturer (like MRC), deigned in the last 15 years would be safe to use. But always check the technical specs. Remember - the same electronics which are in N scale locos (sound decoders, etc.) are also installed in H0 models. Both H0 and N are designed to operate with 12V max (well except for some MTH H0 models). So, if power packs are safe for H0, they will be safe for N.