So are those suggestions what you would recommend for safety? Or the cheapest?
Well now, you're in luck. The Sony's are not only cheaper than some other brands, but are quite safe and pretty much among the best performing
batteries to boot.
It's not like there is a huge difference in price between batteries. $9.50 is a fine price for the Sony's, and that vendor link I gave you is very well regarded.
You can find cheaper on Ebay, but you could be getting recycled batteries, rejected batteries, NOS (new old stock), or worse; a counterfeit. At $9, it's not worth saving a buck or two.
If a vendor or Ebay seller is offering something like a pair of Sony's for $9, it's most likely too good to be true and there is something fishy going down. The prices are what they are.
Batteries are the last place you want to try to save money at concerning vape gear. Batteries are the
only thing about a mod that is dangerous if you think about it.
AW, Sony, Orbtronic, and Efest are the makers of High Drain IMR batteries. The prices are pretty much set, there is absolutely no point in cutting corners here. I can't stress that enough.