Spring clamps are great. On my Sling A/C project, I just went through this exercise. You measure the OD of the hose (in the relaxed state, not over a nipple), and get that size clamp. For 5/8" Gates hose I used 15/16" clamps which were the right size. For 3/4" hose, you'll have to measure.
McMaster:
https://www.mcmaster.com/7329K48/
Amazon also has these.
https://www.amazon.com/Constant-Tens...dp/B0040CYVSG/