Either will work but eSun PETG would be a better choice if the the part will be sitting in the sun on a day like today.
If all you have are on hand is PLA and ABS then I would prototype with PLA as do the final in ABS. PLA will not do well in the sun and heat. ABS does better in heat but does not hold up for the long run in the sun.
The charger puts out a 12 or 24v DC current for a cart or at least that is my assumption, it is fuse protected and the mian AC power is breaker protected. So even if you sorted those metal tabs together it would not burn down anything.
The plastic plug you are printing is there to keep those tabs from touching each other and give you something to hold on to. The other thing is does is prevent you from plugging it in backwards. Charger should be polarity protected but being an ebay unit, maybe not... So make sure you assemble it correctly so the positive lead goes where it is supposed to go.
Have fun and good luck with the design and fabrication!