Easy to find iron plates?
Ivanko or older Yorks with the milled backs. The Eleiko or Ivanko calibrated sets are the powerlifting standard now, but they are multiple 1000's of dollars. Leoko and Schnell are excellent brands, but aren't seen much outside of Europe.
Bumper plates -
Easy to find - Wright, economy Yorks, Muscle Driver/Pendley, Rogue.
Calibrated sets - York, Werk-San, Pendley elites. Eleiko is the Olympic standard, but some of the line the last few years had nasty wear/splitting problems, that they are now fixing. Ivanko bumpers use to crack easily, not sure if they fixed it.
Bars -
Powerlifting -
Capps Texas Power Bar, York's higher end, IronWolfe are all well though of, Eleiko or Ivanko is most commonly seen in formal competition now. Capps Texas is the standard for most powerlifting trainers, gyms, and informal competitions. You'll see them at better meets too.
Weight Lifting - Eleiko, Werk San, Pendley, Yorks higher end are what I'd recommend. There are others that are good, but hard to find in the States.