For the lat couple of months, I've been commuting to a new job and locking my bike in a high theft area. I've been taking my quick release seat with me, but I'm growing tired of this and would like to lock my seat to my bike. Can anyone recommend a good secure method for cheap?

I'm considering a cable lock that I can secure with my u-lock. These go for as cheap as $3 on amazon, but I'm not sure if those are easily broken or not. Is there a minimum diameter I should look for?

Also, what is the cheapest place to find something like that. If anyone can recommend a specific model, that would be great!

Thanks!