Ameetec Arms, does offer a Side-Charging Upper. But it is the Vm-HyTec Flattop Upper,
and they are made of Aluminum. Never heard of a Stainless Steel version.
My info is first-hand, I bought 2 from Ameetec Arms.
Go to " www.ameetecarms.com ",and then go to "Upper Receivers & Parts" 5th item down.
And they are $325.00 with Complete Bolt & BoltCarrier. The Bolt Carrier has a small slot
milled into the front left side, for the Charging Handle to make contact.
Heres a pic from the Ameetec Arms website.