I got the replacement fire extinguisher yesterday. Here are a couple photos for comparison.

The original FA5-1 fire extinguisher is on the left, and the replacement FA5B unit is on the right:



The replacement unit has an aluminum cylinder, a metal valve, pin, and handle which features a metal rivet on the hinge point. This looks like a sturdier higher quality version. It is also noticeably heavier.



Although I'm disappointed that the replacement unit wasn't silver in color, I feel a lot better with this version.