Fred, you beat me to it again… <sigh> ;)
I'd agree that the Cv you're looking for in a 3/8" tube isn't realistic. Try at least 1/2".
Are these valves intended to go on the rocket itself, or on the ground portion?
Regarding a LOX valve:
Worcester ball valves are fairly expensive, and you should use an extended stem. They have electric motor operators as an option, but they're very slow (seconds, not msec). And cost is well above $400.
You could also use a globe valve with extended stem and air or motor actuator, but they'll get expensive too. $400 isn't enough unless you don't want the actuator.
I'd suggest a solenoid valve for this. Try Magnatrol, Parker (Skinner), and ASCO. They should have something in your price range with the features you need. They can be used for the Kerosene too. As Fred mentioned, Valcor certainly can do it as well, and they'd be a good one for a flight valve too, but (correct me if I'm wrong, Fred) they're a bit expensive. If you look into Valcor, I'd also suggest Marotta Scientific Controls, Circle Seal, maybe a few others. They specialize in flight hardware, but they'll be quite a bit more expensive. On the flip side, they can also test your valve to specific g loads and vibration levels, so reliability gets better.
Also, as Fred mentioned, these aerospace valve mfg's often use 28 VDC, but I would think they can also do 24 VDC or maybe 120 VAC.
Just a quick note about materials of construction: the LOX valve should be brass with Teflon or filled Teflon trim. Kel-F, now called Neoflon, is also good. Elastomers won't handle the cold, except for warm parts (on extended stem). Piping should be copper, which you can insulate (vapor barrier especially important). Cleaning is extremely important.