This is the thing - a lot of the “pharmacies” online people buying from are unregulated and there are many, many instances of counterfeit drugs being shipped into the USA even from reputable sellers such as Canada Drugs, let alone the likes of companies based in Asia where most of the counterfeit meds originate.
I think it’s highly likely having said that that an offshore manufactured generic will be what it says but for me that 1-2% risk isn’t worth it and I’ll only go with a branded product which is made in either the USA, Canada or EU.
In terms of sellers out there now which meet these criteria, here are a few (notwithstanding prior comments on CD).
https://www.doctorfox.co.uk/hair-loss-treatments/#_medical_information_tab
http://www.evopharmacy.com/pd-hairloss-propecia-finasteride.cfm
https://www.canadadrugs.com/products/propecia
Personally, based on price, and the product being made for certain in the UK, I’d go with one of the top two.