36 minutes ago, Kraken de Mabini said:
My temptation would be to get the Vivid Vacuum Leak Detector, as it it simple, easy to maintain and works reliably (1). Miso Milivojevic sells them directly (2).
I agree with Elias. A no-brainer to fit a vacuum valve.
As Chris says, you have pretty much all you need. Add clamps and arms. I'd suggest for macro (and copes pretty well with WA too) 2x 8" and 2x 5" arms and (gulp) 6x clamps. I'd highly recommend going with ULCS arms/clamps etc. I've had mine almost 20 years and they're still going strong. A definite case of Buy Well, Buy Once.
Again, as Chris says, the S2000 isn't very powerful but ok for macro. If you plan to buy a second strobe I'd suggest going with something more powerful (say, Inon Z330 or Retra) and then eventually selling on the S2000 for a second whatever you buy for the second strobe.
As the guys say, you don't need a tray - the arms/clamps will do that for you.
Stix floats for buoyancy? Easy to fit, can be swapped between arms as/when necessary. Cheapish (all things being relative!).
Travel weight? Camera, housing, one strobe, arms/clamps, lens - I'd guesstimate at 6-8kgs. Plus whatever bag you use. As Chris says, if you dig around online you can find the weight of most items. Travelling with around 15-20kgs of gear, I'd suggest isn't unusual!