Q: When shopping online for bearings, how do you choose which to buy?

I've never purchased bearings before and I now need about 10 of a
specific size (17x40x12mm, 6203-2RS, double sealed, not shielded).

Googling for bearing quality standards, I find ABEC 3 & ISO P6 standards
are common for bearing *tolerances* for pool pump motors.

But the ABEC/ISO ratings don't appear to cover materials selection,
ball retainer type, grade of ball, the clearance between the balls
and the races, and other manufacturer quality standards.

Worse yet, the ABEC-3/ISO-P6 rating isn't generally listed in most
online ads for bearings when searching by trade size.

Given the same 6203-2RS bearing sells online for anywhere between
$1.21 to $18.99 per bearing, I ask those who have actually bought
motor bearings before ...

QUESTION: How do *you* choose your replacement bearings online?