So a few older Steelseries boards come with BAE, and I've read that they weren't uncommon in Korean boards until 10-15 years ago. There have been a couple of small-run BAE keycaps (GMK Cherry and Signature Plastics DCS, IIRC) recently, but that's hit or miss to find, and if you want the split backspace that traditionally came with it, you need to be careful of that as well.
If the left-shift is less important to you, any "ISO" board will have the right physical layout and you can simply re-configure software and keycaps as needed.
If you want the "US-ISO," it's fairly straightforward, but you'll need to either solder or find a reputable build service. I won't vouch for anyone in particular, but some prominent streamers take commissions, and the mechkbot on reddit.com/r/mechmarket tracks completed trades, if nothing else. There are always a few posters willing to do builds. In either event, you'd just need to have a solderable and programmable barebones kit that supports both ANSI and ISO.
Which brings up the final issue. There are few truly full size boards that are available as solderable printed circuit boards. There is the
Clawboards SUV, which actually shows a build that is not unlike what you want (you'd just use a normal spacebar), but I don't know of any pre-made cases, so it would be a very "raw tech" aesthetic, which some like. There are probably some PCB plans on github that you could have fabricated as well. There was at leats one older project to fit such a DIY PCB into a Filco Majestouch case. Still, if you can drop down to something smaller than a full size, even the slightly compressed "1800" style boards, your options get much better.
Finally, there's always EBay. Converters exist to convert old PS2 keyboards to USB and add programmability.
EDIT: one more option, if you don't mind a short 4u spacebar, would be JIS keyboards. You might pay quite a premium, but
they exist.
EDIT2: At least one
vendor on AliExpress selling "L shaped Enter" keys in OEM profile. Any programmable ANSI could be converted if you're willing to use the slightly unfashionable OEM shaped keycaps.