There are a couple; Brown Aircraft Supply in Florida.
However, on the recommendation of another mechanic, I just bought a door seal from http://www.knots2u.com. It has a separate division called “Aircraft Door Seals” http://www.aircraftdoorseals.com.
I haven’t installed them yet but I like the looks.
There is also an inflatable door seal known as the Bob Fields door seal is now sold by http://www.aeroaccessories.com. It’s a little more complicated but in the past it’s had a good reputation.
Happy Flying,
Steve
