What kind of saddle bag and mounting brackets would fit a BMW Roadstar bike? Do they need to be BMW?

I found a number of them on EBay, they claim to be universal, but I wonder if they would fit, they are all much more inexpensive than the BMW ones, so I wonder why such a discrepancy. Does anyone know?|||Bags fit - same bag is used on multiple makes. The mounting brackets/frames are tailored to the installation. I've used same Wixom and Bates bags on /2, /5 and Suzuki T500 cycles, just had to get different mounting brackets. Current Goldwing saddlebags are mounted with a widely adjustable bracket assembly that has long arms, extra holes and slotted bolt holes that fits couple other large Japanese cycles.|||BMW charges absolutely astronomical prices for their accessories. I bought a used BMW a few years ago, and checked out their helmets and riding gear, because I have matching outfits for all of my other bikes. Insane! Well over $1,000 for a textile riding suit (I paid less for my Alpinestars racing leathers); nearly $1,000 for a helmet without Snell certification. I guess the stuff sells on snob appeal alone. Fortunately, my bike came with the hard cases already mounted.|||there are a large number of aftermarket mfgs who make bags to fit certain bike go to an independent bike shop and ask to look at their catalogs I would suggest tucker - rocky or parts unlimited for a good assortment