For a compact axle wrench you cannot beat the factory wrench and extension handle. 750 tool kits are just about always available on ebay so you could go that route. Other than that, buy a proper sized combination box end wrench. Get one with no or as little offset as possible. It will be too long to store easily, so cut the not needed end off so the proper end is the right length to carry. Now find a piece of pipe or tubing the right size to fit the wrench stub and cut it to the right length to store as well. You've duplicated the factory wrench format now and it should be transportable.