How good is your kitchen exhaust fan? What I'm about to propose will probably require temporarily disabling all your home smoke detectors and could get the rest of your household hopping mad at you.
But those stove top trays can kind of work. But you'll want sawdust, not pellets. Take a separate pan, add a cup of pellets, then slowly stir in water. With light crushing you should be able to make a slurry paste after about 5-10 minutes. Then slowly dry this in a conventional oven, at <150F so it doesn't burst into flames. When it's dry you should be able to easily break it up into sawdust.
Hopefully your smoker pan includes some rack(s) that you can put your fish on, away from the heated surface. Follow the instructions for the pan. You'll need enough heat from the burner to get the sawdust going but you don't want it to burn. Keeping the pan near air-tight helps in this regard. If the sliding lid doesn't look like a good seal, add some foil to it. You want to minimize the smoke leaking out. Run the Kitchen exhaust at the max.
But this won't cold-smoke your fish...the temp inside will probably be hard to keep under 200F. After an hour your fish will be ready to eat. It should have a decent smoke flavor but it won't be like a week in a smokehouse either.
If at any time, things get out of control and you've got smoke billowing and kids yelling, have a quart of water ready. Remove any foil, slide open the pan and pour in the water. Submerged sawdust doesn't smoke, just steams--don't get a steam burn.
And to put this all in context, probably 95% of the general public will tell you not to do this.
