Contemplating pumping

I have been contemplating pumping. It sounds very interesting, and in order for me.
I need some help finding a suitable cylinder at a descent price.
This may seem strange, but I do not really need a new vacuum pump. I have a vacuum pump that I use for air conditioning and refrigeration. I can pull a vacuum on a tank and use the tank for vacuum purposes. I’m figuring, I could just use my refrigerant gauges as well since it has a low side vacuum gauge. The hoses have 1/4 inch fittings however. I can splice a hose if needed. Can an adapter be placed on these cylinders? What size are the threads at the cylinders top?

Thanks in advance,
Stretch 2