as dean said.. used and new valves are available for fitting that COMMON ford top cover ( 55-to at least 75. ) both single and dual spools.
another cheaper option would to hit a hyds supply place and pickup a 2 valve log splitter or loader / generic open center dual DA valve. that will probably run you 150-200$.. maybee less if you find a sale.
plumb the supply and return ports of th valve to QD male ends. on your existing singla DA valve, install 1' stubby hoses with female QD ends.
plug in the plow when needed.. unplug to use the remote for other purposes.
another option is to do the same.. install 1' stubby hoses with female QD's.. adn then get that dual generic valve.. and get a 100$ power beyond plate and mount it under the valve you already have. plumb it directly in and out of the other valve.. and leave that hard connected to the plow.. leaving your other valve for other remote uses. make sur eyou get open center valves..e tc.. either of these options will be cheaper than a used dual top cover valve.. AND give you more use out of your system.
if you have questions.. post back