I used pipe sealing grommets made by Kennard that are flexible. I installed the grommet first, then ran the wires through them.
http://www.kennardind.com/grommets.htm
I bought an assortment from McMaster Carr, on their site search for: pipe sealing grommets.
https://www.mcmaster.com/#pipe-seali...mmets/=1as7odm
Sealsit makes a split grommet. I didn't care for the way they looked and I think they're a bit over priced.
http://sealsit.com/product-category/split-grommet-seal/