First off is the dashing Col Smythe, who seems to have raised several units of Askari. The Colonel also likes to indulge in mechanical devices and the odd hexasaur. Where the funds for these units initially came from is still in doubt, but the troops now seem to be maintained with contracts to various Martian princes.
Another Mercenary unit that has appeared on the scene is the Irish Legion. Funds are reported to be coming from various sources, but ex-American and British uniforms are quite prominent.