Looking forward to Halls, and Pipe-sters answers.
All I remember when i bought my LT500 back in 88 OEM was rubber bushing/sleeve insulator, I went with a Bills pipe and Answer silencer for 15 years with no problems, I just run rubber washers on each side with a Fender washers over that, I know FMF silencers use a Alum/Rubber isolator, on my own projects I looked into these Versa-Mount Vibration-Damping Mounts (Mc Master Carr) http://www.mcmaster.com/#rubber-isolators/=jmt9pq Versa-Mount Vibration-Damping Mounts
 cheap enough, you need a .800" hole for them, been looking for months for smaller ones that you can use a 8mm bolt.

OK, got off the Phone with FMF, and Pro circuit this morning.
 I was asking them on silencer isolation bushings,  reason for calling them was to look for a low cost insulator for some of these aftermarket silencers, they both agreed to use OEM if available or fits, if not use a 0.125" Thk rubber washers and 8mm ID fender washers sandwiched on the silencer would work, preferred would be a some kind of metal bushing (OEM is 8mm ID x 12MM OD x 17mm) or use a partial threaded bolt  (Un-threaded 17mm shoulder)
seems easy, plus an easy trip to your local hardware store.
Unless we  can get SBLT500R to make some nice custom ones?
Bolt / Rubber Washer / Fender Washer

With the OEM bushing

Use a dab of Blue #242 Locktight

Why reinvent the wheel on the mounts. Use the rear OEM suzuki rubber grommet and sleeve and call it good.

The AAEN pipe I had had a small hole for the silencer. I just reemed it out and fit the stock rubber isolator in both mounts. I just figured aftermarket exhaust manufactures would have a rubber isolator that fits there pipe IF it wasnt designed to utilize the stock mounts.

Replaced the two rubber dampening washers with a better set up. Found some *cough* Honda grommets & some sleeves. A few minutes with a die grinder and a file. Much better




Rubber grommet p/n -18334-ka3-830 $2.49 Service Honda
The sleeves I had laying around, no p/n available

The rubber washer and bushing shown in reply #3 will only provide damping in the horizontal plane and will act like a solid mount for vibrations in the vertical plane.  It will only provide the proper damping in the horizontal plane if the spacer is the correct length for the thickness of the aluminum hole  the spacer goes through.   



The rubber grommet shown in reply #9 will provide damping in all planes of motion.  It will provide the proper damping when the steel sleeve has the correct length.