Warlord Games has new plastic bases available.
From the release:
Tired of finding your laser-cut wooden bases are a few millimetres out, ruining your attempts to rank your units up? Not fond of the height of Slottabases? Fear not for salvation is at hand in the form of Warlord’s new plastic base sprues!. The undersides are dimpled so your models will grip uneven or sloping terrain better!