Here is a Tadiran TL4902/T 3.6V 0.5Ah lithium battery:
https://www.onlybatteries.com/showitem.asp?ItemID=20153.148&cat1=51&uid=1724
And at Amazon:
https://www.amazon.com/s?k=Tadiran+TL-4902%2FT&ref=nb_sb_noss
Dimensions of the battery in the GS610:
(as measured, not as specified)
0.956” x 0.554”
(24.28mm x 14.05mm)
Also: See TADIRAN TL-5902 or TL-5902/P