where do you get your parts

[toddfw2003]

I just bought a new Cruise lite. Half the stuff doesnt have a name on it so i dont know where to get the part. I just bought its and there are some minor stuff i need to do. On the shower, lower track wheel connection is broken. I need to order a new on. and the toilet seat. the screen that holds it on is missing. the dealer just stuck a loose screw in. The RV is new. Is a 171rbxl