We've tracked down a source for a reliable, yet affordable, crimper for the Weather Pack connectors. This crimper is American made and truly creates a perfect crimp every time, without the price tag you'd usually pay for a Delphi 12014254 crimper. It's almost identical to the Delphi tool except the price (we've lined em up side by side, looks like they're made in the same factory possibly). Works for 20 to 14 gauge wire, and has a handy plastic block to hold the pins while you make the crimp.
Please note that this tool is not eligible for return once the box is opened.