a couple friends have their own commercial ice machines at their house and haul it. I could go that route you can get a used refurb machine for about a grand. The head alone even less I would think. A 50# bag cost about 17 bucks here. I normally need 2 or three and and have to carry this around and load it on the boat. A real PIA. The payoff is 30 trips. Probably less then one season (not including the cost to run the machine) but it would be great to go down to the boat and open the fishbox and see it 1/2 full of ice instead of carrying ice around in my house/truck/and loading on boat. Also for the long offshore trips where you need ice to the gills you just let her run a few days.
Also the cost to run the machine on the boat is essentially zero. Power and watter comes from the dock...already paid for.
My friends give it to me but I hate bugging them at all hours for ice...I feel like a moocher.