Those Schecters ain't actually half bad. It might be a great way to at least test the waters before getting somethin more bespoke. There really isn't much else out there for us lefties besides the Dug Pinnick 12 string. (Also a Schecter.)
My one other suggestion - if you have a spare Fender body or bass hanging around - is to reach out to Warmoth via email or phone. They used to do an 8 string neck. It's off their website now, but they would still have all the tooling and programming for it. They might actually make one if you call them. They will do 'off menu' stuff on occasion if it ain't too wacky. (I got them to do a gold top, natural back/sides finish on a body that wasn't 'on the menu' in the website.) Then you'd just need a bridge and some tuners. I see there is a Schaller 8 string bridge on Reverb now for less than $100.
https://reverb.com/item/4782134-schaller-s471c-8-string-bass-bridge-2010s-chromeHere's my 8 string with that neck on it....