Most every device I have seen this far is some fossil-fuel driven high pressure pump.
You need to look at more devices. We live on a sailboat and make our own water and every single boat (sail or power) I have ever been on, seen, or heard of that has a reverse osmosis watermaker has an electric one.
Are there electric ones?
Definitely. Some run on ...
There is a nice and quite detailed tutorial on how to do this on Instructables.
They are solving the problem of holding the raft together by using garden mesh. If you have a garden, or know somebody who has a garden, it shouldn't be hard to get your hands on some of this and I'm pretty sure you can use it again as garden mesh once you don't use your raft ...
One possible problem: plastic is usually photo-degradable.
It doesn't matter when you keep a plastic bottle in your house, but if your raft stays 12 hours/day in plain sunshine, it may leak within months.
I had similar experience: the cheap plastic hose I bought lasted only 2 months under Indonesian sun.
Plastic bags can be cut into strips and made into rope of various thicknesses and durability. You could then tie the bottles together.
The boat made from plastic bottles is a nonsense. One day it falls apart and makes more pollution to the environment, than the recycled bottle.
If the boat is motorized, then this could be the source of the pollution too, as the bottle shapes usually are not optimized for hydrodynamics processes and the boat is usually very slow and consumes much more fuel ...