if you want a remot ont he tractor.. you got 3 options.
1 IF you put onthe laoder nad it has a pump.. then just get anover valve bank.
2, if no loader.. thent he EASIEST.. though not the cheapest way to get a rear remote is to buy a bolt on top cover valve. new I believe you will pay 400-500$ easy. used.. half that. simply bolt on and oring placement.. remove the blank cover.. bolt on with new orings. plumb the in/out lines to qd;s e tc.
3, cheapest is to buy a power beyond plate.. sandwich it under the blank cover on your hyd top cover. plumb it to a basic remote valve with qd's probably about the same price as buying a used DA single spool in option 2... with the benefit that you could add other valves if needed.. mind you you are dealing with a max of about 4gpm.. etc.
1 if loader. 2-3 your call. 2 is easy / fast/ 3 requires the palte and a valve and a lil extra hosing. if you just need 1 DA valve. 2 would be my bet.