It seems the batteries I found a ton of on eBay do fit the Jabra A210 units nicely. These are super cheap and are out there by the bucket full. If you are still interested in the bluetooth project involving the "dead" Jabra devices, read on.
I bought 5 of the dead Jabra devices from this link on eBay for $14.99:
I then bought an ac adapter charger for about $4 from another vendor. I don't have that link saved but they are all over on eBay - Search Jabra AC adapter or similar.
I then bought batteries from here:
You can search for other multi-packs of these batteries by searching for "150MAH 3.7V 10C E-Flite BLADE" or similar.
I have confirmed all my Jarba units are functional with a good battery. I can connect and use them as I should be able to. They connect easily enough to the headset etc.
I am in the process of swaping the good batteries out for the new ones. I did also find 3 of the exact replacement batts from a cell phone shop that was repairing some sort of units and they are good to go as well.
So, in the end, I have 5 adapters with new batts for a total of about $35, with a little soldering work. The connections are tight on the Jabra boards but you can do it with a magnifying glass and steady hands. This project may not be for everyone. I will post some pics later of the project in motion.
I did build and test a nice adapter cable using a Cat connector and crimper, 2 wires from the cat (pins 4 & 5 for the Jabra audio out to the FT-897d mic in) and a 1/4" headphone out from the front panel connection into an inline 2.5mm stereo (TRS) connector and it works great. I kept the lengths fairly short but it's pretty easy if you have access to an RJ45 crimper set.
If anyone wants me to pre-make cables like mine for other headsets or your own Jabra project, contact me off list and we can chat about it. I have an RJ crimper.
More to come, with pics.
I bought the inline 2.55mm and 1/4" headphone out connector at Universal Radio. You may find them other places but they were convenient for me.