So far I bought my APAP machines & supplies from,
https://www.cpap.com/
https://www.1800cpap.com/

I prefer 1800cpap.com because they willing to sell to overseas customer without prescription and restrictions. When buying from other US stores, most will require doctor's prescription. Some brands restrict the sales only to the US, 1800cpap.com allow it. Last bought some masks from them in 2019. Things might change, do your research.

FYI and for those who have sleep apnea, here is an US forum I find it helpful for sleep apnea info.

http://www.cpaptalk.com/