As of 2021 I believe they are still unavailable in shops locally and are exclusive to only a few EU retailers. Not sure about the US. I recently purchased a couple of PGs online from Bloom Perfume https://bloomperfume.com/collections/pierre-guillaume-parfumerie-generale which is the exclusive retailer in the UK for Parfumerie Generale. Bloom is offering free shipping for orders above 520 GBP.
But the bottle prices on Bloom Perfume are the lowest I found. Take note that you will be taxed an additional 7% GST for orders above 400SGD. I'm not sure if that includes shipping cost or not. And, your bank will charge a conversion fee, in my case DBS' final charge for my order made in GBP was higher than the initial BloomPerfume's charge and invoice. Thus depending on how many you want to get, you should do a trial cart for shipping cost, add local GST if needed and compare which site is the cheaper option. I chose to order from Bloom because triggering their free shipping lead to signifiant savings compared to ordering from PG's site.