I would either ask your catering service or Google search for ice delivery in your city. I googled for my city and there are a couple but there are minimums and delivery fees. Not a big deal but I'm not sure where I would put 75 bags of ice. That's just the minimum I found for my area.
My husband got a couple of bags and brought them to he venue the morning of the wedding. He stored the bags In the freezer i believe. We had ice for drinks. We just needed some to keep everything cold.
I was concerned about this. My Caterer and Bartending service are bringing ice luckily and will have large tubs to store it. We paid extra for it through it but still probably cheaper than finding a vendor solely for ice.
We were told that ice is a must. We purchased two 150 quart coolers to keep behind the bar for chilling and serving. We will also have three metal tubs full of ice to cool beer and sodas. I will probably ask my brother or close friends to get the ice the day of the wedding- don't want it to come too early or it'll melt- but you need it there early enough to chill certain items. They are coming early anyways to help us set up. The coolers we bought can keep ice for days- which, during the summer, is great. Our caterer told us that we need "sleeves" of ice- which contain multiple bags. He also said you can get these at most grocery stores. We still need to work out the specifics in terms of timing, but we have a loose plan so far. Good luck!
This is recently come up for us as well. We're renting an AirBNB and doing a bbq/pool party the day before for about 25 guests and our wedding will have about 35. We're just going to get a bunch of bags of ice and keep them in the freezer. Luckily the inside freezer will be empty and we won't need it for anything else and there's an ice chest in the outdoor kitchen area so we should be fine. Worst case, we have to have some delivered