I need to replace my battery and I'd like to preserve the radio antitheft codes. Some time ago I saw an ad for a little gizmo that used a 9 v battery connected through the cigarette lighter to preserve the radio codes (and station presets). Now of course I can't find it. Anyone out there know what I am talking about and know ehere to get one? TIA

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Alan Weinschel
2001 S500 Capri Blue
2004 E320 4matic Wagon Tectite
1992 300TE 4matic Black Pearl
2000 BMW 540ia Anthracite