There a quite a few brands of olympic lifting barbells, in no particular order:
Uesaka, japanese, very nice but sharp and expensive barbell (Didn't lift with it, but had one in my hands). Was used at numerous olympic games.
Eleiko, swedish, for many the best barbell ever produced. Was also used at numerous olympic games. Expensive but really really nice.
Schnell, german, very very good barbell from a traditional company. I am personally looking for a used schnell or even better a used berg barbell. These are long out of production but have a legendary status over here (Germany).
Ligo, czech, good quality barbell, many german lifting clubs use Ligo, besides ligo offers some excellent bumper plates. Don't have a webpage but the following dealer sells them:
Leoko, finland, reportedly excellent barbells, see
Pallini, french, makes also a good barbell I was told, but not comparable to the barbells mentioned above
York, american, produces also a reportedly good barbell for olympic lifting.
Pendlay, american, cheap very good quality barbell says among others Mike Burgener, and those who own one.
werksan, american, also reportedly very good.
And then there is the brand of the next olympic games, Zhangkong, chinese,
No idea how these bars are...
I am certainly no expert but have lifted with eleiko, schnell and my ivanko barbell and liked both eleiko and schnell much better than the ivanko ob-20 bar which I own, back in the days when I bought it, it was the cheapest decent barbell over here. I only wish I had bought a used schnell barbell. Then I would be set for the next decades...
The problem with buying used is there are no good deals around. Nobody clear in his mind I guess, sells an eleiko or schnell barbell. Same for Uesaka and Leoko or any better than decent brand.
If money is a concern I would go for pendlay, if you have the cash go for one
of the top brands, even if they are not IWF approved all of the above olympic lifting barbells should be build according to the IWF specifications. For example Pallini cannot affort the fee for the IWF approvement, being a very small family business.
Keep in mind, you will need some sort of platform if you use bumper plates, or at least full rubber plates if you choose to lift without platform...