This quick recipe should only need a 30 minute boil after kettle souring for 16-24 hours; or a 48 hour primary ferment with lacto co-pitched; and/or lactic acid additions to drop PH to desired 3.4-3.8 range.
See below, do whatever you prefer:
http://www.milkthefunk.com/wiki/Mixed_Fermentation#Staggered_Versus_Co-Pitching
Add seasonal frozen and then thawed juice, fruit or puree to secondary to flavour and colour the beer. You could also be traditional and add a fruit syrup to the packaged sour beer, a la the Berliner Kindl.