Sorry I wasn’t very clear: “CTBC financial park” is a kind of shopping center in Taipei Nangang. They have a small 3M brand store that sells all kinds of home goods: sponges, masks, hooks, water filters, … There they sometimes have these masks.
Googling 3M CTBC brings this: https://www.ctbcfinancialpark.com/Shop/Detail/72
The 3M you linked looks different, not run by that brand itself. No idea if they carry the masks.
For pharmacies, both look good. I’d just check a few, some randomly have them.
This is the type I often found: 3M 9501. Made in china unfortunately. It should also be available online at pchome, Ruten, Momo etc. I guess.