need karbonn a5 battery, similar to sg s3 and titanium s2

Hi,
i have karbonn a5 which i bought in 19/8/2012
but now its battery is going bad, it doesn't last as it used to be, and its swelling a bit

so i was searching for its battery in market and found that it will cost me Rs700-800

but i don't want to spend this much for just 1420mah,
so i found that samsung galaxy s3 and karbonn titanium's battery are of almost same form factor as my karbonn a5's battery and have 2100mah capacity

but i am not sure that they will fit in my karbonn a5

so can anyone confirm this that karbonn titanium s2 or samsung galaxy s3's battery will fit in my a5 ?