Tourna Big Hitter Silver and Topspin Cyber Flash are supposed to play a lot like Alu Power.
Pro's Pro Cyber Power supposedly is a copy of Cyber Flash, so that may be a close fit.
Besides that Kirschbaum has brought out a new string called Max Power (also in Rough) which plays very close to Alu Power but lasts longer from what I've heard.
Edit: Nano Vendetta supposedly is similar to Big Hitter Silver so that also sounds like an option.