https://www.amazon.com/APSG-OBD11-Battery-Memory-Computer/dp/B07BLQ9WSS/ref=mp_s_a_1_9?crid=1Y7V9QC6DFSW2&keywords=memory+saver+automotive&qid=1682039951&sprefix=memory+saver%2Caps%2C202&sr=8-9

This is cheap..... But uses 9v batteries.

https://www.amazon.com/OUOU-Cigarette-Converter-Compatible-Etc-Black/dp/B07H179NY3/ref=mp_s_a_1_64?crid=2SMCW1Y50E29R&keywords=memory+saver+automotive+cigarette+outlet&qid=1682040240&sprefix=memory+saver+automotive+cigarette+outlet%2Caps%2C131&sr=8-64

With this:

https://www.amazon.com/SCCKE-Heavy-Duty-Cigarette-Indicator-Protection/dp/B08GGZY82W/ref=mp_s_a_1_16?crid=19O62VPFEJITK&keywords=12v+outlet+male+to+male&qid=1682040348&sprefix=12v+outlet+male+to+male%2Caps%2C192&sr=8-16

You could also modify trickle chargers.

Search "automotive memory savers"

Mechanics use them.

It also depends on how your car electrical is set up.

Feel free to PM me...... I'm not an electrician......but a mechanic that specializes in vehicle electrics.