Thanks for the replies everyone!
I made some calls and found that most marine hardware stores should carry the si/br nuts or can get them in a few days. I think I remember a quote of ~$0.25/each for the nuts.
From my understanding of the posts, I can use regular 5/16", 1.5" long Stainless Steel bolts from Home depot ($0.14/each) with Si/Br nuts to ease future removals.
Nut summary:
Most marine hardware stores have 5/16" Si/Br in stock.
OR
From the McMaster Carr website I found:
Part Number 93439A620
$8.93 per Pack of 50 (only sold in packs of 50)
Nut Type: Machine Screw and Hex Nuts
Material Type: Silicon Bronze
Thread Size: 5/16"-18
Width: 1/2"
Height: 17/64"
Thread Type: Standard Threads
McMaster contact information (LA area):
9630 Norwalk Blvd.
Santa Fe Springs, CA 90670-2932
Sales Desk and Customer Service:
(562) 692-5911
As for locking nuts: I didnt find any that came in Si/Br. (I am going to try the $0.10 lock washers from Home Depot)
Tomorrow, I'll find out how rusted the original bolts are! (Ive been soaking them with PB blaster for a few days).
Cheers!
Patrick