We carry a 25' and a 10' round hose. We've only hit one campsite where we couldn't hook up water or electric, even with our extension cord and extra hose but we were able to switch sites so we didn't have to go out and buy more gear. They all store easily in the rear cabinet.
As for getting supplies: Walmart is ALMOST everywhere, camp stores usually carry potable water hoses (you may pay more but if yours blows out, it could be worth it) and if you have Amazon Prime, you can frequently have gear delivered General Delivery to a nearby post office - it may take two days but if you are far away somewhere, it might be the best bet. We've had equipment and even cat food delivered to a PO on our route and picked it up on the way through.
We like to sanitize the spigot with bleach, then turn the spigot on to flush it out PRIOR to hooking up the hose, tip a touch of bleach in our hose then hook it up to the spigot and flush THAT out before hooking the other end to our rig. It's extra steps but I've seen nasty stuff on spigots and we drink from our taps if we've sanitized the system before going out. When were full time on board, we knew our water supply was clean and good to go.
