We have a fairly heavy-duty head and window pod combo. It's the Manfrotto 700 RC2 head with Manfrotto's window pod.
I assume your Slik tripod has a 3/8" threaded connector as that is what is required to connect this head to a tripod.
See attached pictures It has the 1/4" quick release plate included so you can just leave that on your spotter and quickly snap it in and out of the head.
The window pod is great for when spotting out of a vehicle, and can easily be removed when needed to be used on a tripod. The whole combo runs about $155.00 shipped to a US address.
We also, have the 494 RC2 ball heads by Manfrotto - they are lightweight and they don't have a handle like the 700 RC2 but you can basically use the spotter as the handle. Those go for about $80.00. You can also add the window pod to that as well.
Hope you find what you are looking for!
Shane