with at least 316L. Forget 304 - very crevice corrosion prone - especially where it passes through the deck.

Here is a link to a place where you can buy the stainless if you want to drill your own:

http://www.onlinemetals.com/merchant.cfm?pid=676&step=4&showunits=inches&id=27&top_cat=0

PS. No connection with onlinemetals.com - found this place - not cheap but a place to get hard to find shapes.