Duct tape my neck

I was going to suggest the moleskin too.  I've used it for hiking, and it's the best invention since...well, uh, duct tape.

http://www.drscholls.com/drscholls/productSearch.do?method=doProductDetailsLookup&searchArg=67

My only concern would be that the water caused it to come loose from your skin and rub just as bad as the wetsuit.

I've used large waterproof bandages and that worked well.

However, I've never been able to get BodyGlide in any quantity to prevent neck rash. I use SportShield roll-on instead.

In this case, I would liberally roll large amounts of SportShield onto the wetsuit neck itself, then lightly glide it over the bandages.

Good luck.

Depending on how large the area you need covered is, you could also try liquid bandage. The dark bottle with the little stick brush built into the cap, not the Band Aid kind with the q-tip applicator.

Start applying it in thin layers over the top of each other a few days before the race so you have a nice thick cover by the time you need it.

Might not work as well if the area is too large or needs to flex more than the liquid bandage can handle. However, it should be fairly waterproof.

I'm new to the Tri world, but I have been a surfer for years....we use a kind of undershirt called a "rash guard" which protects your skin ( get it at any surf shop).  It is one more thing to take off during transition, so you may just have to put up with the hickeys....some people find that petrolium jelly works well too. 

 -Good luck. 

PS, don't duct tape your neck...but if you do, take a picture of your skin afterwards and post it.  I'f b curious to see what it looks like.