So whilst browsing Google+ one day (yes, someone still uses G+!), I discovered a wargamer playing with some paper miniatures, printed on their normal printer. Just simple silhouettes of modern soldiers, but effective enough for proxies on the cheap.
So I decided to go one better, and 3D print my own equivalent!
With a bit of practice using Inkscape to turn bitmaps into SVG paths, and importing those into FreeCAD, I managed to make some perfectly serviceable troops.
They are printed in 2 pieces, the dude and the slotta base are separate, and they snap-fit. Took around 50 minutes to print 8 dudes and bases, which is a very tolerable time if you need an extra squad in a hurry! I estimate the price of the plastic at about 12p for 8 of these guys, so definitely a cost effective way to boost a force.
You can find all the relevant info for these guys on Thingiverse if you have a 3D printer of your own.