I have installed catfish and set up a Thunar custom action for it. It works very nicely for me. You could probably set it up as a Dolphin action on KDE4 as well, if you want. Here's the custom action for Thunar:
- The hard way:
edit ~/.config/Thunar/uca.xml and add the following before the last </actions>:
<action>
<icon>catfish</icon>
<name>catfish search</name>
<command>catfish --path=%F</command>
<description>search with catfish within current directory</description>
<patterns>*</patterns><directories/>
</action>
NOTE: Something I learnt the hard way: It's no use prettying up the code in uca.xml, as Thunar mucks it up again into a single long line the first time it uses it...

- The GUI way:
In Thunar, select "Configure custom actions" on the Edit menu, click on the "+" icon to add a new action and fill in the blanks:
Name: catfish search
Description: search with catfish within selected directory
Command: catfish --path=%F
Appearance conditions:
File Pattern: *
Appears for: Directories