What I am calling the lower control arm is also called the swing arm, part number 33326770744, it's sold at $599 on FCP Euro. If you check ECS Tuning they tell you that these bushings are not replaceable, even though we know they are. They had these control arms form $533.

I got under the X5 again and tried to measure the bushing bore size in the control arm while not disassembling anything yet. Not the most accurate method by any means, but the range was 49.5-50.0 mm with some calipers (around 1-15/16" & 1-31/32").