Recommendations for solar powered battery charger

[aww999]

My LS400 only gets used rarely and sits on the drive most of the time. I would like a solar powered battery charger to keep the thing alive, as it's not convenient to keep putting my trickle charger on it. (When I say not convenient, I mean that I keep forgetting to do it until I need the car.) There are lots of solar powered chargers available, can anyone recommend a decent one? The car just has the standard factory alarm/immobiliser, and had a new battery about a year ago, so this shouldn't be too much of a challenge for a charger to keep up with.