I have two Alinco DJ-C5 radios that I use both at home for fun and at work
for monitoring business frequencies.
It's kind of the joke/rule of ham radio, you never, ever, buy a battery
from the company that makes the radio, no matter who makes it. They are
almost always at least double what the same battery costs anywhere else.

Safety/reality check:
The Alinco battery is built into the radio. There is no battery pack,
this is the 'credit card' radio with built-in battery.

This means that replacing the radio is easy: remove two screws,
take off the back cover.

The more serious issue (VERY SERIOUS SAFETY ISSUE) is that it's a
LiIon battary. Charging these is a lot more difficult than NiCd/NiMh
and wrongly trying to charge it could cause the thing to explode.
For this reason, the charger is specially built and doesn't easy fit
on other transceivers.
Don't try to charge LiIon cells on NiCd chargers w/o good fire insurance,
I don't know about the reverse.
At any rate, the voltage/capacity rating of the original pack is
probably very difficult to find with NiCd cells so stay with LiIon.

This is freaking me enough that I'd be very careful replacing it with
a battery of the same capacity (and probably size).
I think you will find that the market for replacement LiIon batteries
is a lot more complicated, for the safety issues above; you can't just
replace them easily.

In that light, $48 for a replacement is not that bad though still
expensive. Check the service manual (which is online), but I'd
consider the original replacement. I suspect you had plenty of lifetime
from the old battary.

Hope this helps, 73

Geert Jan PE1HZG