DS7 has run through most of the available kits. But recently, I have been collecting bits and pieces of real lab equipment from a variety of sources. I haven't pulled this all together into a lab kit for DS. But he is going to be giddy once I do!
Most universities have a surplus store where you can occasionally snag stuff.
But I have my best luck with used lab equipment sellers. Most of the time they are very friendly and helpful. And they are excited to see kids doing science I have even occasionally been able to borrow more expensive equipment short-term for a fancy-ish experiment. And they have all the little extras like pipettes, stir bars, parafilm, etc. If you happen to be in Northern California - here is my favorite:
http://www.scientific-equipment.com/homeOne more thing. You can get a huge amount of reasonably pure chemicals from household stuff. You just have to know what stuff is made of. We recently did an experiment where silver was deposited out of silver nitrate solution onto the inside surface of clear glass ornaments. It took some fancy reagents, but the only thing I had to buy was silver nitrate (from a local high-end camera shop), The rest came from random things like, crystal drain opener (NaOH), splenda (sucrose), and Walgreens brand hand warmers (ammonium nitrate). Here is a list of chemicals you can get from readily available products:
http://makezine.com/setting-up-a-home-science-lab3/ Note that some things are out of date - e.g., you can't buy ammonium nitrate fertilizer any more. But you can get it in certain brands of hand warmers. Just google around and you'll be amazed at what you can find.
