I bought one of these from Amazon about 5 or 6 years ago when they were having a "buy one get one free" special. I believe it was around $5 back then. At 4' long, it's the perfect size to connect the filter canister to the city water inlet and hang the filter on the rear bumper of the trailer. Now, Amazon is charging around $10 for the same hose with no "free one included"...
https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1
This hose along with a 90 degree brass coupler are "perfect" to connect the hose without excess strain on the trailer plastic water inlet fitting.