if you don't have an enom reseller account or similar, you can use someone else's free domain search form. It will open to their site, but the one below is neutral enough that clients probably wouldn't leave often.
Paste this (and correct the < and > if it gets messed up):
<table BORDER=0 WIDTH="300" BGCOLOR="#E6E6CC" >
<tr><td><center><b><font face="Verdana" color="#3333FF" size=-2>Add
this FREE Form to your WEB site -<a href="http://www.chandigarhcity.com/domain/freedomainsearch.htm">
The resulting page will give them a banner that is used by the company supplying the form ( http://www.chandigarhcity.com/domain...mainsearch.htm ) but visitors won't really know it's not your client's. They even give you a way to link back to the site you came from.