Thanks for your ideas, gentlemen. As I said, Glengarry 5, I don't want to be messing about with serious conversions (head swaps are about my limit).
I've never bought a box of Perry ACW figures, and not having a need for them, doing so would make the exercise not only time consuming but expensive and wasteful, too. I do have an unrelated use for GB plastic Arabs though, so if I ever chance upon a box going cheap I'll grab it.
Sometimes you have to articulate a question in order to self-generate an answer, and a little bit after the fact posting the above enquiry jogged a memory that there's some information on Sudanese slavers in the Chris Peers Foundry Darkest Africa books, from which I gleaned the following picture:
The book says that slaver forces were multi-ethnic and costume was heterogeneous, and indeed the illustrations show a variety of clothing, from knee length Turkish-style breeches worn with a shirt tucked into them and a fez, to a knee-length 'blouse' worn with fairly close-fitting ankle-length trousers and a turban, to a hooded cloak very reminiscent of North African garments worn by the Berbers and Arabs of the Maghreb. The text says that many Khartoum slavers looked very similar to those from East Africa, whether 'Arab' or Swahili. Like the Zanzibari Arabs, the Arabs of the Sudan were of mixed Arab and African blood, so even the faces of these figures are accurate. No doubt the Sudanese look, as epitomised by the various Perry packs mentioned above, was common, too.
All this got me thinking about what I already have that would fit in. I have a substantial painted Zanzibari collection, so I suppose I could just use those figures straight without too many historical accuracy qualms, but to keep the Sudanese slavers distinct from their eastern counterparts I think the mixed effect suggested by the Foundry book would be preferable.
I have some Indian Mutiny figures (mostly OG, with a few Foundry) awaiting the brush. Some of the OG matchlockmen figures are costumed virtually the same as the slaver standard bearer depicted in the Foundry book, and the others look much like the Perry Mahdists with their robes worn over the shoulder and one side of the chest bare. Maybe the dhoti is a little un-Sudanese, but from three feet it should pass as breeches, and although the book says that muskets were usually flintlocks or percussion ignition, I think it's the fact that they're muskets, some being loaded with a ramrod, that is the more important and visible aesthetic factor at tabletop viewing distance.
Mutineer infantry in native costume should be visually acceptable; at least the ones without too much hair (so the OG mutineers are out). Their white dhotis and shirts should look very similar to the figure in the Foundry book in 'Turkish' costume, and the ones I have are all in either skull cap or turban. The officers even wear short, zouave/Turkish-style jackets over their shirts.
Did slavers have bayonets? Probably not, generally speaking, but Rabeh Zubair was a former Egyptian army officer who seems to have tried to impose a more military regime on his forces than you'd encounter in a typical slaver army.This tendency might conceivably have extended to the equipment of at least some of his troops.
A few of my Foundry Baluchis in Indian costume should blend in well enough; again, the ones with minimal visible hair.
For the breech-loader equipped minority I plan to mix Zanzibaris with the Foundry DA Azande in Arab-style (Sudanese, really) clothing I have stashed away.
Cavalry isn't essential, and anyway, I do have a few Redoubt Moroccans in djellabahs that would suffice to represent a small scouting unit.
As is obvious I already have more than enough 'shooty' figures to field a Sudanese slaver army. As I seem to have trouble generating the old spending urge these days I'm very happy about that. I might still pick up a box of Perry Mahdists to add a few Sudanese-style riflemen to the mix, but mainly for spear and sword-armed warriors to supplement the shooters.
If I was starting a Sudanese slaver army from scratch I think it would be quite an enjoyable exercise looking for suitable figures to throw into the mix. In addition to the options listed here you could include Artizan Design Moroccans (but not Tuaregs; veiled slavers are highly unlikely), other North African tribesmen in hooded djellabahs, such as those from Askari Miniatures and Rif Raf (now Burns) Miniatures (but not the ones in straw hats), other Indian Mutiny brands such as Mutineer Miniatures, the aforementioned Barbary corsairs, and… well, I'll leave that to you.