"If anyone has had a similar need, what did you do?"
Go to Salute and browse all day? You'd probably be able to find all sorts of useful individual characters from various ranges.
Otherwise;
Hasslefree and Heresy both do very nice characterful fantasy figures -- all available as singles IIRC.
F15s do several lots of fantasy figures; link for example. They also distribute Eureka's ranges. Most of those are available as singles.
Em4 do packs of prepainted characters; link and also unpainted singles.
Black Cat Bases have figures which may be useful.
Mithril do LotR figures individually.
And, of course, there's your local GW for their figures, and your local independent games store. Ours stocks the warmachine/hordes ranges, and the character figures in there come in individual blisters and can be useful.