Cheapest route is a couple long hydraulic lines hooked to your rear remotes. Downside to that is that if you had something hooked to those remotes you won't be able to use them at the same time. Second downside is it's much nicer pressing a button on the fel lever to operate the grapple vs letting go of the fel lever working the rear remote lever then back to the fel lever etc.
What Kspring61 posted up is a beautiful way to finish it up, potentially nice that you get to use all 3 functions at the same time.
I went with the electrical diverter which is the other common route - a press of the button on the fel lever switches between the bucket control and the grapple control. I love it, works really slick.
I built it up myself - I see you're from Ontario as well - I sourced most of what I needed from Princess Auto. The Hydraulic switch was from there, a bit over $200 for that. (You can find it on sale occasionally) I never did tally up the whole bill but for sure all the hydraulic adapters/fittings you have to buy add up to a surprising amount. (Hydraulic hose itself wasn't so bad! But the fittings...) A wild guess mine worked out close to $600 I think? That includes the grapple I made myself. That's Canadian dollars fyi. The biggest pain in the butt was getting home realising I'd got the wrong hydraulic fitting for something... Having to go back... swap out fittings... That happened more times then I care to admit! At least Princess Auto has no issues with returns. Lol!
E.