Instead of looking for high alpha acid substitutes for noble hops, you should stick with noble hops for flavor/aroma additions, and instead use the high alpha acid hops for bittering.
For lagers, I like Perle, Clusters, Styrian Goldings, Northern Brewer, and Magnum for bittering, in about that order. In the past I have tried varieties like Galena, Santiam and Vanguard for bittering, and found them to impart just enough American hop flavor to be distracting.