On Fri, 10 Mar 2017 18:13:53 -0000, "Gareth Magennis"
wrote:

I am having difficulty finding a 1/3AA Lithium battery.

They are called CR1/3N or CR11108. Search for that, and you'll find.
If you can find them with solder tabs, however, is another matter.

It is for this application, any substitute has to fit in pretty much the
same space as 1/3AA, there is no spare room.
http://wolzow.mindworks.ee/analog/jx-10-m-16c.htm

It looks to me like this battery is used only for keeping the SRAM
data alive. If so, the current draw will be very low. If you can find
a smaller 3V cell, that will still work for a long time.

You could also stack two LR44 cells. The size should be about right.

I did find rechargeable NiMH types, but I don't think they will keep their
charge for the years expected of a memory backup battery?

Rechargeables are not the right tool for this job.

Perhaps I could utilise watch type button cells, if I could find a holder
for them.

That is a good idea. If you can find a combination of holder and
battery that will fit, that would be a good solution. You could look
for both dual 1.5V or single 3V solution.

Looking at the device, it does not look complicated at all. Are the
high prices because of the collectible value, or would people be
willing to pay similar money for a new, compatible device?
--
RoRo