bicycle seat post plug 30mm

if you have to leave your expensive bicycle out in the rain and snow you will nead to protect the inside of the seat post as well as the rest of the bike from moisture i used to use a plastic tarp over my bike but because it is a trike i cant completely tie the stupid thing down to the bike the wind always blows it off so i have given up on that thought and every month or so i spray the whole bike with wd40 to prevent rust and i mean every thing tires chrome brakes everything i thought that this