Lego Help for my 5 Year Olds CN Train

Hello Reddit! I am hoping that this very smart group could help me figure out how to finish a train for my 5 year old. I've tried my best, but a Lego engineer I am not! He loves Lego, and I bought and collected up most of the pieces for the CN Train from Eggy Bricks, but a lot of the parts aren't available, or I'm having trouble finding. I wasn't able to find the battery pack so I improvised to keep the body steady, and I tried attaching other wheels to the bottom from the holiday train but...