This might be a candidate for pulling out the "Search" component of the page into a user control and adding a "Search-Mode" property to it.
You can have different search_X.aspx pages with different output/styling/gridview columns etc...
and you could define your control on each different search page with a different Search-Mode
e.g.
<myctl:Search ID="searchCustomers" runat="server" SearchMode="CustomerPurchases" />
or
<myctl:Search ID="searchCustomers" runat="server" SearchMode="CustomerDetails" />
Then have your page bind to some event on that control that gets back the SearchClause/DataSource etc for binding to your display list