I’ve been looking for bumper plates myself for when I put a home gym together and unfortunately have found that they are very expensive over here.
You could try the Australian Barbell Company, their stuff is usually very good quality and I do remember that the price of their bumper plates was quite reasonable compared to overseas brands, probably because there is no international shipping costs.
Another one I came across recently was a fitness supplier on E-bay called Cyber Market. You will find them under the strength training section. They have bumper plates for $4.50/kg which is about as cheap as you will get them over here.
Now, I don’t know what quality they are but there is a warranty so if you do lots of lifting I’m sure you will find out very quickly if they will fall apart or not. I will most likely go with this seller as my budget is very limited so cost is the overriding factor, plus I don’t lift that much with the O-lifts yet and thus won’t be dishing out too much punishment to the plates as I can still mostly control the weight on the way down.
They also can source a high carbon steel Oly bar with roller bearings for $265 which you will need fo O-lifts to save your wrists. Once again this is the cheapest I have found.
As they are in the same suburb I live in I am hoping to get along to their show room in the next few weeks to have a look at the equipment myself. I could let you know what I find if you are interested.
If you find any cheap O-lifting equipment yourself please let me know!