Recommended source for replacement traction batteries?

The least expensive car to own is the one that's paid for.
ALL cars will need replacement parts eventually. Still less expensive than a new car.
When you factor in car payments and insurance, if the car is still in good shape, like you say it is,
it's worth putting the money into it. Because you like the car.
If you take your time, replacing the battery won't be that difficult.

 

If we’re going down that road then the least expensive car is one given to you for free. You didn’t have to make any payments on it

 

Have you red those “installed battery with reversed polarity terminal” threads?!

 

No, I haven't. I really just can't understand how anyone can do that. Even if you just GUESS, you have a 50/50
chance of getting it correct!
Like I said, GO SLOW. Pay attention to what you are doing.... It is NOT hard.

 

Has your battery failed? If not just leave it alone.