Thank you everyone in this thread. After reading this thread, I've successfully replaced my battery for the HP3468A with a
1/2 AA Tandiran SL350P which is what I could get from Farnell UK at the time.
I guess it must be easier than putting in a 2/3 AA. With a half AA, you have a lot more room to work with and the leads are easier to solder in compared to solder tabs I think.
Before I did anything, I had a bit of oh @!&* moment when I accidentally shorted the battery - I realised that within 5 seconds. There was no spark, flame etc. and the temperature of the battery did not increased noticeably, if at all. But the voltage of the battery went down to 3.2V (3.6V nominal, 3.7V when I first tested it). It gradually came back to 3.65V after 10 minutes or so. I wasn't sure how much damage I did to the battery, and didn't think straight, used it to replace the old battery inside the HP meter.
Now when I think about it, I start to worry about the longevity of this new Tandiran - Should I be worried? should I get another one to replace this??
Any comments are welcome, TIA