Where can I buy an instrument for measuring blood oxygen in Beijing?

I have switched on and off the oximeter before, but I remember seeing it in a Norwegian wheelchair shop on the west side of Pok Oi Hospital. I forgot what brand. If you have time, you can go there. That's where I bought my wheelchair. The service is good. Besides, the wheelchair is still very easy to use. Neighbors want to buy a ... Baidu map after reading it.