You can in fact get a 100 watt solar panel for close to $100.
SunElec.com You will also need a PWM controller, but they are also much lower cost these days than even 5 years ago. Find a 100 - 150 watt solar panel that is not to large to fit between the stuff on your roof, and you can go days without needing a noisy generator.
My 1994 solar panels are still working great! They tend to last more than 30 years, though nobody really knows how long they will keep producing power. Many think they will produce about 70% of their original power until they are well over 30 years old, and will keep putting out at least 50% even when 50 years old! I really look forward to being able to measure my solar panel output in 2094 when they are 100 years old, but I don't know if I will be around that long!
Personally I would rather not listen to my 400 watt solar system than run my generator for 10 minutes a day. Most campers without solar tend to need a generator for over a hour per day on average.
Fred.