Thracian and baestarne merc's- you can find thracian merc's in western asia minor macodonia and epirus and sometimes Illyria. I've only ever found baestarne merc around Byzantium and in thrace itself
I just saw some Bastarnae significantly farther North than that. Can't remember the name of the province, but it starts Rebel between southeast of Germania, Just North of Dacia.

Anyone know where there's a map?

If there are more than these I've never seen of heard of them.
There's a couple Camel mercs to be found down in the southeast corner of the map. Bedouin Archers and Bedouin Warriors.

Also, Spanish mercenaries, Barb Cav Mercs.