I'm not sure how to post a link but type in Neoteck 9999 in Amazon. That one looks pretty good, has some nice clamp type test leads and even does temperature. Way more than you need but I would say a good value. I'm sure Home Depot or Auto parts store would have something as well. You are looking for something that will measure milliamps and if it has 10 or 20 amp capability even better. It would probably be best if you measured and verified the draw at the battery before you go to individual circuits though. Maybe some of the guys who have a battery switch installed could chime in with what they get for measurements since the battery switch makes it super easy and we would have a good reference point.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)