You and me both.
For pilots, you might try any of the 1/48 plastic ranges like Tamiya - some of their traditional pilots might work with a little conversion. But the build would be quite slight compared to the Monolith range, which are quite chunky.
I've yet to find anything really good for the feral humans. If you're a member of the Monolith Yahoo group you'll have seen the ranges for 'Prehistoric Europe' - some possibles there, but nothing really 'caveman-y'. But if you do a bulk order of all the apes, apparently there's also a chimp figure available.
But unadvertised. For some reason, new releases are never posted on the Monolith website - you have to join the group and rely on pictures of greens being released in dribs and drabs - a load were promised a couple of months ago but nothing has materialised. It's a weird way to run a company, as if they actively want to deter people buying their stuff. Which is sad, because the figures are really excellent. I'd buy more if only I got the impression they wanted my custom!