170PCS Rubber Grommet Firewall Hole Plug Set Electrical Wire Gasket Wonderful
https://www.amazon.com/dp/B07BK1DY9F/?tag=atomicindus08-20
Swordfish 21100-180PC Closed Rubber Grommet Firewall Hole Plug Electrical Wire Gasket Assortment Set, 7 Sizes
https://www.amazon.com/dp/B07PBN6F4K/?tag=atomicindus08-20
Smaller sets / pieces available. Search "rubber grommet plug". Or ‘wire gasket’. Maybe that helps
Lemme guess - packout related?
Question - if your trying to pass a wire + plug through this, is it just once, or do you want to be able to pass it through - back and forth? If its just once - to leave the plug outside a box - you should be able to use stretch the grommet (with small hole for wire) around the plug, and install. The back and forth - you’ll probably just have to use a solid plug and slit the window down the middle.