You could use brazing rod if you don't have silver solder but silver solder is much easier to work with....no flux needed. But the brazing rod is way less expensive.
I wouldn't try using common plumbing solder though because it might not be strong enough.
Just hold the plug upside down clamped in a vise on the hex and carefully chip out the porcelain with a small punch or chisel.
Cut off the hex with a die grinder or Dremel with a wheel.
Cut the threads off of the nipple and then solder the plug and nipple together.
I made mine for a 2006 BF 20 D but it fits many other Honda models too.
Good luck.
