To close this thread and provide info others may find helpful.
I found a suitable rechargeable CMOS battery (ML1220) at Alexander
Battery on Spruce St. Had to get it ordered in. $6 each. I bought a
spare, as they come without the lead and tiny plug, so I had to unsolder
leads and solder to tabs.
Found a couple of YouTube videos on tear-apart of 1005HA. Not too bad.
Unfortunately, have to disconnect both keyboard and touchpad ribbons.
Battery was shrink wrapped with protective material -- I used electrical
tape. Bluetooth antenna also had to be taped down. Not a very tidy
interior, nor easy to access things. e.g., there's a ribbon cable across
the hard drive. Sigh. I didn't have to touch that.
Worse part was touchpad ribbon, as the keeper popped out and fell on
floor despite great care (the ribbon flipped it!). Took about 20 mins of
crawling to find. Other than that, OK.
Now working fine.
JN