I have used www.partsurf.co.nz in the past when I needed a new dock assembly for my 3GS.
Nathan there is a great guy, more than willing to help. He insists on only using geniune / quality parts (except in the case of some batteries I think - in any case he is very transparent about what he is using, just ask). Unfortunately no connection to Hamilton but definitely worth a look.
I got mine from slickdoor.com you can only buy the front and back though but it's very cheap. I paid around $60 I think for new parts. They ship from China so it takes up to 3 weeks which is a downside but I've had their parts on my phone for over 6 months with no concerns or worries. The home button is also included in the kit.