jzodda
Are you handy?
This isn't the easiest thing to do and even harder to describe without pictures!

I saw an article on the net about 6 months ago (I can't find it right now..looking...) and it was how a guy was using a Peltier I believe and the tab had broken off the socket.
What he did (and this supposes the area around the tab is more or less free from Capacitors ect.) is to lay down a 3" X 2" thick layer of 5 minute epoxy (if you have a larger area use it) and then let it dry hard.
You don't need to worry about any traces shorting as he mentioned the epoxy is non-conductive.
After you have a nice thick hard layer directly under the broken tab and extending a little ways around the M.B., take your nut for the Peltier attachment and cut a small piece of steel that is about half the size of the clear M.B. area and attach it to the nut with a cutdown machine screw so it only goes half way into the nut.
Now you have a nut with a small steel plate attached and half the threads still available to lock the Peltier down. Mix up some more 5 minute epoxy and put a layer on the dried epoxy area of the M.B. and also coat the bottom of the steel plate and put the bolt and plate in position where the tab use to be.
Layer on the epoxy over the steel plate (don't fill the nut, leave a long bolt in it in the right position), let it dry and repeat about 5 times until you build up a good thick layer, then let it dry overnight.
When you attach the peltier you may need to build up washers on the bolt to get the right length as you only have half the threads available in the nut.
Remember the Peltier doesn't have to be tight...just snug it down and according to the article the guy found it was nice and strong.
Any questions let me know.