You could make your own :
- create a text file with some fortune content
with a blank line containing only '%' between
each block of text, say name it 'myfortune'
(add a % after the last text block)
-copy this file into /usr/share/games/fortunes/
(for slackware fortunes databases are here)
-create the .dat file :
strfile /usr/share/games/fortunes/myfortune
This way you added your own fortune, you could
explicitly call it with :
fortune -a myfortune
[edit]
also I found this one for download fortune databases :
http://freshmeat.net/browse/895/?topic_id=895
enjoy