hifi engine

Replacement Bass Drivers for Pioneer S55X Speakers

I need to source a pair of the 8" bass drivers used in the above early 1980s HiFi Speakers. The originals have the part no 20-749B stamped on them, and are rated at 35watts RMS and 6.3ohms impedance. I don't have an up to date address/phone no. for Pioneer UK or their authorised spares distributors, but it is possible these drivers may be obsolete, since they are over 25 years old. Can anyone help, please?