You could buy add'l. FR figures for your units. They have two figures that are standard bearers specifically, and there are other open-handed figures that could be used. Most of the men at arms figures could pass as commanders IMO.
To be honest, last time that I looked on the FR site, I couldn't find the standard bearers and officers

so I will definitely get that set but I will still be wanting some more variety. The primary set of rules that I will be using will be Hail Caesar and my local group uses units with a frontage of 120mm (2 figures deep) so I want most of these to have their own command, just for aesthetics.