The Solid Solutions rubber grommet looks ideal. However the lamps I used will not fit quite as easily. The H7 connectors are trapped inside the lamp and the lead to the LED driver/ballast block is not especially long. It could be connected as Solid describe but I felt it was easier to splice into the three wire lead that goes to the lamp body connector. That gave more space to access the connectors and still allows the originals to be used with halogens if needed.
The bulbs I have are shorter than the Solids. This puts the heat sink half into the lamp casing. If the OEM cover were 10mm taller they would totally enclose my heat sinks. Not a good option IMO so I cut the tops off and used the rubber/neoprene/proofed nylon "washer" to seal around the bulb stem. Rubber grommets would do the same job and give that little bit more clearance around the heat sink.