I need to charge multiple systems a week with about 1.25 lbs of r404a quickly (30 mins or less) and consistently. We have a 0-100 lbs scale but that only works for weighing the tank before and after as simply moving the hoses throws off the measurements. Is there a product for this? I've seen glass cylinders on ebay that seem to be for this purpose but they don't make new ones anymore and they aren't for 404a although I'm not sure that's a problem as long as I can consistently fill them to the same level.