Dry Hopping in the Keg

I want to try dry hopping my kegged and cooled Pale Ale. I know there are lids that have a special hook welded to them to hang a hop bag but I don't have one of those.

How can I hop in the keg without buying one of those special lids? Doesn't the hop bag need to be suspended in the keg? I wanted to try pelleted hops so dumping them in really isn't an option. I thought about using a thin gauge fishing line but I didn't know if the lid would seal or if I tried to tie it to the dip tube, if it would stay in place. Thoughts?

I just toss the bag in and fish it out with a sanitized wire hook. You can use the line. It doesn't matter if the lid doesn't seal, you aren't trying to carbonate.

Actually my beer is already carbonated and cold. It has been kegged and in the fridge for about 4 weeks now. I just wanted to add more hop aroma and hopefully some hop taste to it.

I had the thought about using a plastic wire tie to attach it to the dip tube.