One wasn't found right away there when browsing. But these are low cost items available at different vendors other then newegg. One can been seen for $5.99 at http://www.directron.com/dir80120.html
One site that specializes in cooling devices as well as fans and adapters is coolerguys.com where a pair of lower priced adapters are seen at http://www.coolerguys.com/fanadapters.html
I already responded on the thread seen there about the 4.32 version seeing problems. Getting a good 80mm to 120mm will certainly help keep temps down with an increase in air flow especially on the prebuilds with the limited space for using larger fans. But I could easily advise HP ar least over eMachines if planning a new one like seen in your sig. You wouldn't want Dell either according to one thread started at that make! http://www.computerforum.com/81163-dell-hell.html