Looking for power cord/brick for apple designed powered speakers M6082 made in 1993

Those speakers use a 15-volt, 1-Amp DC power supply that has a Sony type barrel plug on the end. A Sony plug has a center pin in it (as shown here), that inserts into a mating sleeve in the device's power port. Most devices are the opposite, having a power port with the center pin and a power supply plug that has a small diameter sleeve in the center. Assuming that the dimensions are correct, you could buy a Sony power supply (any voltage) having the correct type/size plug and remove it along with a reasonable length of wire still attached. Get a 15-volt, 1-Amp DC power supply (many Altec Lansing speakers use that) and attach (solder) the short section of wire with the Sony plug, so that the plug's center pin is connected to the DC power supply's positive output (typically it's the center sleeve, but not always). The polarity is indicated on the power supply label. On the Apple Design speakers' power supply, the center pin is positive and the outer barrel is negative.