Best place to buy batteries for fixed wing?

Where’s everyone buying their batteries nowadays?

I have a stack of lipos here at home but they’re all fairly old (>5 years) and I’m wanting to renew pretty much all of them as I don’t really have much confidence that they’re any good. I’d hate to put a new build together only to have it fall out of the sky if the voltage sags.

I normally use or but I know the latter are out of business now?

And… is it best to use lipos nowadays or are 18650 LiOns a better shout? For reference, I’m talking about flying a Mini Talon and a Skywalker 1650 so if I remember rightly they’d need to provide a max draw of about 40A on a 10" prop at full throttle on a 1400kv motor and maybe 5-8A sustained.

I used to go with 4s 5000mAh Lipos although the Skywalker used to take 10000mAh packs in it no problem, so I guess anything in that range would be ideal.