I think I made mine out of Honda Civic wires for the old carburated motor back in the 80's. Bought 10mm wires and shorted the coil end of the wires to make a custom fit set of wires. You can remove the coil end with a pair of needle-nosed pliers carefully open the crimped metal ends. I elected to cut out the top cover of the plug cover to allow the wires to pass thru as it is easier than removing the cover to diagnose problems quickly. Forget pulling that stupid cover every time you want to blow out the plug holes or check for spark. I cut it out so as to still kinda shields the plug wires but still be able to pull the wire off the plugs. Here is how I did mine.
The length of the plug wire is about 2 inches longer than stock, about the height of the cover, so they are all the way down on the plug as well as sealing off the hole in the cover.
The cover is not sealed well to the head, you should inlarge the holes where you can pass the seal thru the cover and seal the aluminum holes of the head. You don't have to make the holes as large as the rubber seal, just get them large enough to squeeze the rubber and pass thru the plastic cover.