If you already own a "Weber" grill or similar you could try what I did.
I bought one of those little single electric burner hot plates from Walmart $9.99
I then enlarged one of the vent holes at the bottom of the grill to be able to
pass the electric cord plug through.
You place the burner at the bottom of the grill and place a small old cast iron
skillet on top. Then set the temp low/med/high and place wood chips in the fry pan.
Like cyanide said, electric is easier becouse heat stays constant and you don't
have to watch the grill so closely.
I've smoked fish in the winter doing this and the grill maintained a constant 200deg
temp.
The nice thing about this is you can use the same grill for both types of cooking
and not have another cooker taking up space on the porch. Something to consider?
GM