hard to find screws

i purchased a used boat with a carpeted floor which i suspect there is a plywood subfloor, it has 2 aluminum pedestal bases with 8 phillips oval head wood screws that are rusted, they need to be replaced, looking for stainless steel, local lowe's or Home depot has them in 1/4" dia but the heads are too small a diameter,no where near whats on the boat now, where are these screws available probably something about 1 1/4" lg
chet

 

If you ever operate your boat in rough conditions, you should look into a better method of securing the seat pedestals to the floor. If the existing screws are rusty, there’s almost certainly been water intrusion, which becomes rot over time.
You can bore some test holes to check.
If you’re confident that the floor is still in good condition, some SS toggle bolts might be stronger than screws.

 

There are specialist bolt and screw suppliers, you might find some on the net, and their catalogue.

 

I am buying everything at McMaster Carr