WORKAROUND:
It is not possible to do this using the Find and Replace activity, but it can be done using the editor.
1. Open text file in Editor.
2. Press "Ctrl + F" to invoke "Find and Replace".
3. Click the regular expression option, enter Find context, and then replace.
STATUS:
Waiting for enhancement ID 'QAT-2635' to be released in a future version of Toad Data Point.