In the usual spirit of, 'If you want it done properly, do it yourself.' here's what I did.
Purchase a decent quaility double throw waterproof toggle switch so it can be on or off depending on the way you choose to wire it - I know a single throw could be mounted other way up but you can guarantee sod's law will prevail at some point. Get a wee strip of stainless steel slightly wider than the switch and file a curve into one end. This strip is going to be made into a guard. Make a cardboard version of this first to get the sizes correct. The other end of the steel strip has a hole drilled into it of a size to suit the switch thread. The steel guard (strip) is going to be mounted on the front face of the switch mounting surface - switch through panel -> steel guard -> washer -> switch nut.
Right, now you need to bend the strip forward at 90 degrees so it pokes out from over the top of the switch, next you need to bend the strip downwards so it protects the toggle in the up position - the filed curve allows tricky access to the toggle should the switch be (inadvertently, of course
) put on without the cord and it needs to be switched off again. The switch is activated by a kill cord of your choice and needs a loop over the toggle before it is switched up behind the guard. The loop can be anything of your choice, wire, metal clip, keyring, the loop on the cord end etc., and if you're incapable of making a suitable clip you shouldn't be let out onto the ocean in charge of a boat! IMHO!
Plainly, the dimensions have to be reasonably accurate and that's where your cardboard comes in to play. The top off yer cornflake packet will do fine for that.
And you'll have the added satisfaction of pride in your work...
And, in willks case, the pleasure of outdoing the customs man!