I have had the craycourt Weber insert since Dec 2010 and really enjoy it on my Performer. Recently I've picked up a couple inexpensive used kettles; a 22.5" OTS for $10 and a very good condition 22.5" OTG for $30 on craigslist. I'll keep one of these at home as a back up to the Performer and have taken one to my office where I have a small patio area. I found these char-broil universal cast iron grill inserts at amazon.com which supposedly fit the weber (picture below). I ordered the last one they had in stock and it should be here early next week. It's 1/3 the cost of the craycort AND ships for free with prime. I'm looking forward to seeing how well it works.
http://www.amazon.com/dp/B009LHILCM/?tag=TVWB-20