My initial order of Impetus-sized bases from Litko arrived recently:
These three bags will be enough for 45 Impetus units! These are very nice bases.
I do have another worry - what sort of adhesive should I use? Having 7 to 10 metal minis on one base will get a bit weighty; I can not hope that, even with the 3mm base, the units will always be handled by the base - some one (probably me!) will pick up the unit by one mini and I would prefer that it not break off. I might need to use the hot-glue gun that is hiding around here, somewhere.
The base color is another item to consider. I typically use craft paints for bulk area painting, but my usual base color - Territorial Beige from Apple Barrel - is too dark from the dry scrub look that I want to portray (it works great for a more temperate area), so some new paints will be on the shopping list.