[Test-Equipment] Tektronix DM-5010 Battery Replacement

[Dale Smith]

The battery in my DM-5010 Multimeter died the other day.  I am in the 
process of looking
for a replacement.  I know very little about batteries and charger circuits.

The service manual gives the following information

BT1121  146-0037-00  Battery Storage:2.4V, 150MAH (Page 9-6)
(From the MSDS this is a NiCad battery:
http://www.tek.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/Service/msds/&FrameSet=service )

and

"This +5 volts is also applied to R1131, charging the battery BT1121
when the instrument is operating." (manual change c2/981 page 32)

If any one has found a suitable replacement, any information would be 
appreciated.

The only battery which I found to be close is from Radio Shack:
http://www.radioshack.com/product/index.jsp?productId=2102704&tab=techSpecs
This is a 650 mAh battery and I don't know if it would work at this charge 
level of 5V.
The size is simmilar to the current battery in the PI.
Current
31mm long  15mm diameter
RS
26mm long  22.5mm diameter

Again any help would be great,

    -Dale