I use the same as Bruce. I buy them from All-Electronics quite cheaply in 2 wire for power and 3 wire for sound.
Connecting locos for MU can get a little tricky. If you follow the Aristo method, locos only have one type (either M or F I don’t remember which) on both ends of the loco. This is fine for plugging in your trail car that has the opposite plug, but two MU two locos you need to make an MU cable. Aristo’s method has the advantage that it doesn’t mater which way the loco is facing. If you were to wire a loco with M on one end and F on the other, then they could only be connected facing one direction, unless you also have gender changers on hand.
You need to check the polarity colors on these 2 pin plugs. The ones from All Battery come wired different ways depending on the batch.
I had one odd situation when setting up MU that I had to reverse the polarity between locos in order for them to both run the same direction. I had wired the locos so I may have made an error somewhere - don’t remember the exact situation but I have in my collection an MU cable with yellow ends to indicate that it swaps polarity end-to-end.