http://www.ebay.com/itm/Sony-Hi-MD-portable-walkman-Lithium-Ion-Battery-LIP-4WM-/270607993813?pt=Batteries_Chargers&hash=item3f017e4bd5#ht_1840wt_1185 I found these on eBay but when you say "it involves quite a bit of work", do you have to have special calibration equipment or could a skilled IT tech conquer the job OK? They have them for < $10 att his link, Vs. $38.xx from Sony, don't understand WHY they change 1 # and chare 3-4 X's more for it, I guess it all comes down to supply & demand!