977L adding a 3rd valve

I have a 977L (48J)
I want to put on a brush grapple on my cat and need to install a 3rd valve, if anyone has any leads on where to find the parts I would highly appreciate it. Or if someone has idea’s to control the hyd. Rams on the grapple someway else by adding a pump or plumbing into the hyd system and using a remote valve

Thanks

977L adding a 3rd valve