Though, if you have a specific vision, Best to just design yourself
My vision for the Imperishables was based on much of the existing GW range (bad idea I know given that it's out of production), so unless GW do something amazingly fantastic like bringing all the 8th Ed plastics back for the Old World, I'll have to make do with the best that I can find. I won't be making a Nehekros army for a long time yet because I've got a lot of other projects on hand for Warhammer Fantasy and 40K at the moment, but I've had a rethink and have come up with the following solutions to making most of the units:
Nekaph, Emissary of the King: I had a crazy brain wave of using Syll 'Esske as the basis for the new Nekaph, if I ditch the Daemonette on top and base Nekaph around the massive human mortal with the axe. I'd have to abrase off the tattoos on his body and his nose ring, replace his axe with skulls on chains for the flail and try my hand at greenstuffing to give him some more Egyptian apparel, but most of that shouldn't be too much trouble and after I would paint him up as a stone statue, he'd look great as Settra's bodyguard.
Embalmed King on Warsphinx: This was a difficult one, but Lost Kingdom have developed a really nice one. Are their Tomb Kings stuff 3d-printing files or actual models? Because the prices look very cheap to be for fully-made models.
Embalmed King and Mortuary Priest: Mantic's Empire of Dust range has a metal kit that can be used to build either a Tomb King or Liche Priest each time, so buying a few of those would give me an Embalmed King and several Priests to guide my legions to victory.
Settran Legionnaires: I think the Mantic Empire of Dust skeletons are the best bet here, as I based the Legionnaires on the Tomb Guard which are now OOP and though Mantic's range is halfhearted and mostly metal, the aesthetic is the closest to the plastic Tomb Guard. The Revenants and Archers can be used as Legionnaires with Halberds and Bows, and Legionnaires with Khopeshes can be kitbashed using the Skeleton Warriors and some metal Khopeshes from Crocodile Games, who sell a lot of Egyptian-themed metal stuff.
Necrolith Onyxites: Crocodile Games' Sebeki crocodile-men are based on 25mm square bases which translates to 32mm rounds in AoS, so they'd make some cool animated statues when painted in the right colours.
Necrolith Ushabti: Mantic make some metal ones, which are a bit chunkier than the GW ones and maybe not as detailed, but they're not bad and are highly affordable.
Mortuary Scorpions: By far the easiest to find alternative models for. Reaper make a good Giant Scorpion in their Bones range, as do Wizkids. Won't have a problem finding a few of these.
Legionnaire Warsphinx: As with the Embalmed King on Warsphinx, Lost Kingdom have developed a skeletal War Elephant with skeleton crew that look like Tomb Guard for their take on Tomb Kings, that fits the role of a Legionnaire Warsphinx quite well, though the skeletal elephant is of course not a stone construct.
Necrolith Colossus: Txarlifactory make a good colossus model that harks back to the old metal Bone Giant. They also make their own take on Legionnaire Duneriders and Sepulchral Stalkers, but those are sold out and I don't know if they'll be making any of those again.
Necrolith Heirotitan: Norba Miniatures used to be quite good at making Tomb King models, but since they changed their material to their new plastic, they've got rid of most of the stuff they made for Tomb Kings. However, the one model they have remade in their new material is their great Heirotitan model, which looks decently affordable and fits the description perfectly. Apparently Norba have a reputation for poor customer service, but it'd be worth it just to get a single Heirotitan for a Nehekros army sometime down the line.
Settra is the one thing I'm really struggling with for proxies, because my vision for him is so specific and unique. Someone else got close to it with this Tomb King-ified answer to Katakros:
But my ideal model of him is big enough to take up the whole base by himself to be around the same size as Nagash, doesn't have all the familiars around him, and is ideally posed like the Incarnate Elemental of Fire:
But with the Blessed Blade of Ptra instead of that fiery staff, and his features of course looking like a Tomb King. Perhaps I'll have to bite the bullet and look for Tomb King bits on EBay to make my vision of Settra, I was certainly visualising the pharaoh Necrosphinx face as Settra's face, and perhaps one of the Necrosphinx blades as the cutting edge of the Blessed Blade.
