Did a search and haven't found where to buy replacements.... 2 fell out after MOT inspected the bulkheads.
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http://www.heyco.com/Hole_Plugs/product.cfm?product=Liquid-Tight-Plugs-Standard-85§ion=Hole_Plugs
Certainly you will need to measure the diameter of the holes you have.
Another option is to use a good polyurethane to adhere a square of aluminum or FG over the area.
THANK YOU! ! These are the ones put in at FT or MOT before I got the coach..
Will get under there and measure . but I think they are the normal ones used.
Or maybe use clear lexan or plexiglass so you can see if any more water worked it's way in?
Head over to one of those ACE hardware stores with hundreds of parts drawers, and you will likely find your round plugs.
YESSIR! Ace is the Place!!!
buck a pop and in stock.....1 3/4" hole plugs