If you want a cheap magnetic drain plug, get one for a BMW car they are less than 4 bucks shipped on ebay.
The size is 12mm x 1.5 I ordered one while waiting for the kits to be restocked.....if ever?
Update, the BMW car plug is to long to fit the super 8 engine.......So I cut it in half used red and black high temp jb weld and installed it in the filter screen cap, works great fit in the cavity of the cap perfect.