My first ever was a DAT Walkman TCD D3. It had a specially designed NiCD Battery. The first time it needed to be replaced, I was able to purchase one, second time I was out of luck.
It seemed that Sony wanted to let DAT die as quickly as possible to replace everything with MiniDisc in the late 90s.
Yep, Sony wanted to rush out a newer format and cease any real backup for previous formats. The change from DAT to MiniDisc was a retrograde step audibly IMO, DAT with no audible compression to MD with ATRAC compression. I said no thanks to MD and stuck with DAT. I went for Tascam, a good choice of format and manufacturer - however as with all old formats the consumable media eventually becomes unavailable.