Congrats on the new ride! I went to eBay. I bought a detachable sissy bar and backrest used for under 150 USD. I bought a five bar rack for 76 USD. A big savings from the dealer. I also bought premium touring luggage (largest one) for 230 USD (new). I spent under 500 USD for the whole kit and they were mighty appreciated on the ride up to daytona last weekend. The dealer told me it would cost me 1000 USD or so for new.
My suggestion is used from Craig's list, eBay, etc. I did troll ebay for a while before finding the deals. All parts were in great condition or new. I did have a minor blip when a parts seller sold me the wrong rack (FXSTSSE2 has a 200 mm rear tire). I had to send it back and it cost me wasted time and 17 bucks return shipping which he did not refund. I found the good rack a few weeks later, all before Daytona.
Tip: don't bid on an eBay auction. wait until the end and bid then.
Ride safe and welcome to this awesome riding experience!
Carl