There are several different versions of the gust lock, depending on model year. You can always get one from Cessna of course, but last time I checked, the price was outrageous, I recall something like $400. You could manufacture one from scratch and have it silkscreened for less. (that would be legal too, under the owner manufactured parts rules)
Best bet to find a used one is ebay or barnstormers.com just keep in mind that they are not necessarily interchangeable from one year to the next.
