The Parasailor is made only by Istec.
For a L500, I would have thought you'd be looking at 150-185sqm depending on how adventurous you are and what wind
strength you are planning to use the sail in, as well as factors like whether you plan to leave it up overnight when sailing downwind across an ocean etc.
I came close to buying
a 160sqm (as recommended by Istec) for my L440 but ultimately had a 155sqm ASI made for a third of the price
. Different sails
for sure, but deep down wind
sailing over very long distances is not curently my task.