Didn't many of the Turcomen use ancient chainmail and other antiquidated stuff? Maybe not enough of them were in full ancient dress, but some did, as I recall.
So, you may find some proxies to at least bolster your force.
In the old ESCI, new Italeri 1/72 plastic "Muslems" set, there is a figure, with some chainmail and such, that is argued to be a Turcoman or even a Crusades era warrior. So you could get by with a bit of fudging.