Hoses can be made in many configurations of end's and exact lengths. I'd say buying a "set" of JCB hoses and thinking they are gonna work on a B21 kubota has a zero chance of working.
Take hoses to a local shop and have made exact, or identify the size and type of ends, measure the length, and use any one of a dozen online sources
Ford 3910, John Deere 420C, Kubota G32XKS, IH 2606, Bad Boy Maverick-60"
The only drawback to Surplus Center is their pre-made hoses are mostly in 1-foot increments. If you can get by with a 36" in place of a 30", or similar length differences, the hoses are high quality at good prices.
I use DiscountHydraulicHose for hoses by the inch. They're a little more expensive than SurplusCenter's hoses by the 6" (for short lengths) or 1' increment.
Tying a string to the BH hose you're replacing is a good idea.