Something that small and that important I buy locally. Open the yellow pages and look up springs. There are local shops that build/rebuild springs all the time. You can bring your old bolts/plates there and in a short matter of time have it done probably for less than shipping costs.
I have gone to the local spring shop for mine, usually because of the typical incomplete lift kit. [img]images/graemlins/mad.gif[/img] As mentioned above, grinding a bolt head round has worked for me too in a pinch.