I, too, had the exact same issue as you with warping rotors every 5,000 miles on my 99. I feel your pain...BIG TIME. I finally bought a set with a one year warranty from Napa and I've gotten about 7,500 miles out of them so far with no shimming. If they do within one year they'll be seeing my face again.
Don't waste your time looking for braking products from RSM. If you look at their site, they don't sell rotors for 1997, 1998, and 1999 model years. I emailed them and asked them what'* up with that and they told me they were too busy to investigate.
Furthermore, their site lists rear rotors for a Bonneville. LOL. I'm yet to find a Bonnie with rear rotors. I don't put much faith in those guys.
If you have the money to shell out, I'd go with the PowerSlots.
I agree with the comments about THROUGHLY cleaning all the rotor and wheel mating surfaces. I used starting fluid to clean all my surfaces (since it'* the closest thing to pure alcohol) and a wire brush. Furthermore, I let my lug nuts soak overnight in a clean coffee can full of 10w-30 Castrol. Don't use WD-40 as it'* a solvent, not a lubricant.