My local Microcenter sold their last 2020 this week. So I don't know of a source.
OWC has Apple Certified Refurbished with the i5 and they have ACR opened for upgrade for the i7s. If you find a place that sells them new, please let me know too.
There is a nice used 2017 for sale nearby, i7, 500 GB SSD but I'd really like a 2020 for macOS updates.
I just noticed OWC’s as well, it’s $1,049, not bad.
I bought my new i5 3.3ghz/8gb/512gb ssd from Woot in December for $940. I don’t see too many brand new ones listed since, but just last week they had an open box (newish) for around $750.
If you find a good price on Amazon, the official 3rd party certified refurbs have a decent return policy if you don’t like the condition it arrives in. I tried out a 2019 that was around $720 but I hated the Fusion Drive and wasn’t willing to deal with opening it up to replace the drive.
You could also try FB Marketplace, deals vary wildly depending on your market.