Most hotels also have universal plug adaptors that the front desk or housekeeping can let you borrow. Otherwise, there's bound to be a shop near the hotel that sells them for a pittance--even supermarkets often have them so no need to find an electronics or home improvement store.

As said above, nearly all electronics' converters cover the range of voltages so no need for transformer there. Good hotels will have shaver points in the bathroom for 110v. The only appliance I can think of that a transformer might be needed are electric hair dryers/curling irons....get a dual voltage appliance before you leave or (for extended or repetitive travels in China or 220v countries), just pick up a single-voltage 220v appliance in China.