Battery trays are all over the place...you can get the battery tray for under $20 here.
When you're talking about the fender light dying, do you mean your Valiant has the little turn signal indicators mounted on top of the fenders, and one or both of them no longer flash? If that's the light you're talking about, you can either spend $3.40 apiece at Year One for a replacement bulb with a plain brass base, or you can spend $10.60 and get a 10-pack of non-corroding nickel-plated ones as a part of your shopping spree to buy upgrade bulbs for the rest of the car's lights
(see this post )If by "fender light" you mean the sidemarker light on the side of the fender, in front of the wheel, the upgrade bulbs for those are covered in the post linked above.