Victoria Miniatures has quite a range of GW-styled models that are generally a better fit with older Citadel models. You can combine these with a variety of other third-party heads like those by MaxMini for example, to get a nice Chaos look without needing them to be festooned in Chaos star symbols. Personally, I think the Arcadians
with some of these heads
from MaxMini would look great. Victoria also does Beastmen
too. Pricey, but I guess you only need a few.
For a less organised militia look, you could also look at the Frostgrave plastic kits put out by Northstar. These capture the raggedy-barbarian look very well, and come in Cultist and Viking flavours too. Plus there is a Gnoll set too, which could make a great basis for some different-looking Beastmen. If you just want one sprue from a box (each box contains four identical sprues of five models each), I have seen various ebay sellers who will sell them like that. Plus, Northstar do a sci-fi weapon pack
to upgrade the plastic kits with.
Beyond that, there's loads more stuff actually. If you can post some examples of what you're actually after, it may help with further suggestions.