Union Electronics (UED.net) was the last to have them - Russell Industries made a replacement, POR-10H. Note that all the Sony numbers for 7 or so models all cross to the same part number, 1-501-156-99 or 1-501-156-XX (XX=don't care in Sony lingo...).
https://www.ued.net/ued/viewItemActi...e=SNY150115100
I have one of the POR-10H, New in the package...$22 + Shipping. PM me if interested.
BTW, most appearance parts were dropped by Sony after 3 years, thanks to the cancellation of the FTC "life or 7 yrs" rule" from the 60's... Sony stocked electronic parts sometimes for more than 20 years past their prime - the SG-213A is an example - deleted in the early 00's.
Cheers,