Direct pull brakes are very simple, (as long as they're not the absolute garbage plastic-over-steel variety, with plastic levers, and they can be adjusted properly) you'll not get a major improvement by changing the arms. They might look nicer and have better hardware, but you'll generally only get minor weight saving because they need to be stiff, and that requires a certain amount of metal. The only really standout V-brake was an old XTR model that had a parallelogram arrangement to keep the block faces flat with the rim as the arms moved over, but you're unlikely to find them, if you do they'll likely have worn pivots, and they weren't really all that anyway..
Proper fitting/maintenance, good friction material and good cables make the most difference.
There are mini-V brake arms generally intended for use on touring bikes with narrower tyres and road levers, apart from that they're mostly the same geometry with minor variations between models.