Pemko has the tools and products you are seeking
I have been looking for this myself for a few weeks. There are actually two places you can buy it, the company mentioned in the This Old House article cited inan earlier reply and a company from California called Pemko. Pemko not only has the tools and materials for kerf-in weatherstripping, but they also have the special tools and materials for metal interlocking weatherstripping. Check Pemko or Resource Conservation Technology out and you will be very happy. These two weather stripping styles are extremely effective, and there are many new kerf-in products available from other manufacturers, like All Glass Parts, Inc as well as from these two companies.
Bill Dorsey