Normally, for a tool I’d use once every few years, if that, I’d buy the Harbor Freight version. I want to order the cheap Amazon equivalent as I don’t feel like driving 30 minutes to HF.
Related: the Transit forum recommends this vacuum fill device as it’s difficult getting air out of the complicated Transit hoses when changing coolant.
You can use it to check for leaks by seeing if it holds vacuum but a pressure system may identify the location of a leak such as a particular hose.