I have used the OXO silicone pads in addition to connecting the return pump to the hard plumbing with a short section of silicone tubing.
Here is a link that shares others similar responses:
I got this at BRS so I assume it's ok but I can't find much about it anywhere else.....have any of you used it or know anything about it? http://www.bulkreefsupply.com/silicone-vibration-silencer-oxo-good-grips.html
www.reef2reef.com
Good luck with whatever you choose!