Hi, I found that for new stuff Rio Grande or Metalliferous were
preety good… depending on what spec you need. For second hand stuff
ebay is great. As for a casting machine … I made mine from a large
metal box (welded air tight by a friend) with a hole in the top for
a perf flask and a vacuum pump (from ebay). The investment table you
can just buy a side draw bell jar (from Rio Grande or whoever) and
some rubber and a nice chunk of marble / granite from a stonemason
… this works well!