What site is alipay.com?
You should be on this site.
https://www.aliexpress.com/
Once you place an order a pop up window appears to enter cc info.
Here is the page with the suntour seatposts
https://www.aliexpress.com/wholesale?SearchText=suntour-ncx&origin=y&d=y&isViewCP=y&switch_new_app=y