i noticed that the plastic brackets are very easy to break and found these but they only seem to be in the US so if anyone can find them in the UK they should get a medal. =P Anyway with all these adapters being metal you might as well do metal all they way heh
http://www.coolerguys.com/840556062097.html
As you can see the Metal bracket is designed to take AMD/Any other HS's but also can take the normal p4 HS's so it would be perfect to adapt for a stronger hold down XD