Roofrack delete -need help sourcing out the parts

[ukrcan]

I know a few on here have done a roof rack delete. Everyone keeps talking about using some sort of plugs to plug the holes after removing the roofrack, but for the life of me, i cannot find them in the home improvement store...I am starting to think they don't carry them here in Canada...
I know i need 8 11/16 and 4 5/8... but what exactly do they look like, are they plastic or rubber? which department could I find them in? I've tried explaining what i need to the store staff but they couldn't help me either...
Does anyone have a picture of what it looks like? or maybe a sku number?

I know i would need to use some silicone for a snug fit, but is this a reversible mod. Will i be able to put it back up if i need to?

Thanks much!