Founders World in Shinrarta Dezra is the only station in the game guaranteed to have all ships and all parts (all at 10% discount). However, it requires a permit that you can only get by reaching "Elite" rank or by being one of the kickstarter backers.
Shopping around for ships and parts is one of the challenges in the game.
There's a random factor to which stations have which ships and parts. (faction specific ships will only be available at stations controlled by that faction) You'll find a slightly different selection if you visit the same station at another time, even. Prices will vary slightly between stations, too.
Your best bet for a wide selection of ships and of high-end parts is to visit a large station in a high population system with a high tech economy.
I'm on PC, not Xbox, so I don't know the actual buttons to push.
Go into the galaxy map. Go to the view options. Set "Show by color" to "economy". Uncheck everything except high tech. Set "show by size" to population. Zoom out a bit. You should now see a galaxy where most stars are greyed out, the high tech systems are the only ones visible, and the bigger dots are the higher populations. Select a likely target system, select the system view (concentric circles with dots), select a likely station, and verify that the station has both outfitting and shipyard facilities.
With the current PowerPlay factions, there's also a 15% discount (and possible supply boost?) for systems controlled by Li Rong-Yui. Bigger discount than the harder to get Founders World discount. There's view options for PowerPlay in the galaxy map, but you can also (via left panel) go into the PowerPlay info, select Li Rong-Yui, select Control, select one of his control systems, and click a "view in map" button. Try to find a high-tech system he controls.
Even with all of that, it often takes 2 or 3 station visits to get everything just right. If I'm shopping for a new ship, I'll throw the biggest FSD I can find into a hauler, and sell the hauler at my destination (after confirming I can get the ship I want and an FSD upgrade for it). Make sure your new ship has enough jump range to get out of the system you're buying it in! If you buy a new ship, can't get it out of that system, and can't buy a FSD upgrade there, you're pretty stuck.