You have
EDDB - Elite: Dangerous Database, which allows you to search for bodies providing a certain material (even within range of your current position, so that is really nice), but it doesn't list the percentages contained on these systems. You can look up the material logs, and deduce a little about the available percentage based on these numbers. You also have the
Elite: Dangerous Star Map, which can list you the Jumponium Rich Systems, a.k.a. The Galactic Highway (and if I may add, also the galactic by-way

), but again no numbers on the percentage there yet.
I think that the "monster sheet" could tell you a little more on percentages. You can read all about it (and about prospecting in general) in the
[DISTANT WORLDS] Cartographic & Prospecting Public Service [NEW] thread.
I think it is just too soon for tools to utilize the percentage listing that is now available in-game.
Fly safe That you may find many a rock,
CMDR Jermus
(Who thinks that a system with 1% Polonium is worth noting down <scrabbles in notebook/>)