Looking for source recommendations; hydraulic flow control valve and waterproof junction box

Hi,
I am hoping some readers of this group could help me source two items;
if such questions are inappropriate here, please let me know. I have
been web searching but if anyone has recommendations I would greatly
appreciate it.
The first thing I am looking for is a hydraulic flow control valve;
something a step-up from the average back-yard water valve. I have
heard of precision control valves that have knobs that can be locked
down (similar to calipers). I'll consider these but am also interested
in electrical control (I already have flow meters for feedback and am
thinking about a closed loop). 4 flow valves with flow meters built in
that can be programmed independently of any other hardware would be
idea.
These valves will pump water (10C warmer than room temperature) at
rates between 5 and 15 gallons per minute.
The second item I am looking for is a type of waterproof junction box
that I have only been able to visualize thus far. I would like
something with a clamshell-type design so that I could open it up, have
a device placed in it with two wires extending out of the box, such
that the box can be sealed. I am picturing two grommets, each cut in
half, that split apart when the box is opened, creating a seal when the
box is closed, but I am unsure if grommets will work decently in such
conditions (?).
The box will be exposed to dust, salt, and temperatures up to 80C.
Quick removal is key. I am planning on attempting to build something
like this myself if I am unable to find anything on the market.
Thanks much,
David.