Gotoh 201B-4 C Bass Bridge

More substantial than the traditional Fender bent-metal bridges, but it still keeps the look mostly traditional, so if you're looking for a more solid bridge without changing the optics of your instrument too much, this might be for you.
Standard Fender 5-hole mounting, standard 19mm string spacing, so it's a drop-in replacement. Hex-key and mounting screws included. The small hex screws on the saddles run in grooves along the base, so there's less side-to-side movement of the saddles.
Personally, I don't hear much (if any) sound-difference on my P-Bass compared to the stock Fender bridge, but your mileage may vary if you're more sensitive to tiny differences.
Tiny annoyance is that Gotoh felt the need to visibly put their company-name on there... so keep that in mind if you're particular about that kind of thing.