My regular doc and pharm (Kaiser) supplies me.  Should be covered with a prescription by nearly any health insurance.  If yours is recalcitrant, get the scrip and check GoodRX.

Their other products are sold in CVS and advertised on TV so they are certainly subject to FDA scrutiny.

I don't have a significant other, so I generally go through my general practitioner who has prescribed ED meds at my request.

But during my most recent prostate exam last month, my urologist recommended Mark Cuban's new costplusdrugs.com for really good prices.  

The 5mg tadalafil I use daily for BPH is crazy inexpensive -- 90 pills for $10.40. That's 80% less than GoodRX and Blink, and anywhere else I looked.  

And the 20mg sildenafil citrate (90 pills also for $10.40) is also hard to beat. I usually use two or three 20mg pills on game day. My urologist suggested I switch to the 50mg sildenafil citrate, which runs only $12.20 for 90 pills. They also have 25mg and 100mg options (the latter can be split, of course).

I will definitely use costplusdrugs.com next time I have to refill.

I don't have Kaiser, but a friend did, and a few years ago he used to get 20mg sildenafil completely covered by his insurance.