I found such an amplifier on Aliexpress. It was attracted by the meager price (12 rubles) and miniature sizes. It is a ready-made module for two channels, dimensions 18x21mm, power 2.5-5volts, output power 2x1.5W (with a load of 8 Ohms) and 2x3W (with a load of 4 Ohms). Since during the operation of the amplifier the heat dissipation of the elements is very small, it can be placed in any closed case without fear of overheating and failure.
Cost: ~ 16