How are you going to use it? Dry camping or mainly parks with full hookups? You can buy stove tops with ovens, or just the stove top if you won't ever use the oven, that gives space for storage or a microwave if you would use that. Same with the frig, it all you want to do is weekends you can get a tiny one and save more space. You have a blank slate (albeit a small one), before you buy think about what your lifestyle will be when using this. The appliances, toilet, etc. are available from any place that sells rv parts, Camper's choice, Camping World,
etc. The brand names are rather limited, the market is pretty specialized. You can also try marine items, but they can be pricey sometimes.