Hi Dave,
Pretty easy to make your own. I built one out of 100mm diameter ally tube.
This one has 2x #10 fittings on the top. There is a baffle inside that forces the air/
oil vapour down the side of the tank and out through a perforated section. This helps separate the
oil out before the air goes up and out through the filtered breather at the top.
This one holds about 3L or so. I've got an #6 fitting on the bottom that has a cap on it for a drain but I'm setting it up to run back ito the sump via a 1 way check valve.
I've made a coolant catch tank in the same style and removed my old header tank. Preciously at track days I had a soft drink bottle taped to the front X member for a coolant catch bottle (10 out of 10 for rat rod style). I've machined up and welded a filler neck direct to the water pump and the pressure cap is on there now. The coolant catch tank is set up with the inlet/outlet at the bottom so coolant will suction back to the motor as it cools. The coolant crossover between the heads also burps to the top of the filler neck as the highest point in the cooling system. The system fills really easy.
Hopefully the whole setup looks more racey than ricey
Cheers