orienteer

Halfords, or probably cheaper on ebay.

There's no adjustment, just tape over part of the front of the lens. Easiest to buy a kit at under a tenner, includes diagrams for every car.

My son's MX5 is on my drive while he is abroad. I have to charge the battery every 2/3 weeks, it has a Toad alarm fitted. Where do you keep the car? If garaged leave it unlocked, it needs the chipped key to start it. Or lock it manually with the key so the alarm isn't set. Another option is to leave it on a trickle charger.