Ryan - I thought that I'd also occasionally replace the fittings or keep spares, none of which seemed to pan out when I needed to tie something down while underway and all I could find were rusted fittings :-)
Anyway, we make our own tie-down fittings now; basically a piece of 1" stainless all-thread, parted off in 3" lengths, drilled & tapped for 1/2x20 with a 3/16" thick x 3" dia. stainless flange welded on the top.
Drill a 1" hole in the deck, bedding compound under the flange, drop the all-thread through and come up from the bottom with a backing plate and 1" nylock.
Here's a few pics of the tie-down fittings, the latest version doesn't have the counter-sunk holes on the flange, they proved to be overkill...
For most tie-down jobs, I thread a forged eyebolt into the fitting, hand tight, no tools needed, no moving parts to corrode;
I do have some specialized fittings that I can thread in for special jobs related to my industry.
Now, some of the items that I need to secure on deck weigh 6,000 or 7,000 pounds, so the 1/2" works good for me, the items that you'll be securing are significantly smaller, so you might be able to fabricate a similar system using 1/4" fittings and eyebolts.