Thread on BYB
Another thread on BYB
I am 23 yrs old as well and have researched before deciding on a breeder for my puppy - if I hadn't found this breeder I would have just got a puppy from the RSPCA or an animal shelter.
Maybe you will find a lab x border collie at a shelter - the problem everyone has is that you are looking for a cross breed dog and unfortunately will be most likely supporting someone who continuously breeds for money without caring about the animals that rely on them.
There is no guarantee that a lab x border collie will be similar to your boy.
I know that you miss him and love him but please consider finding a responsible breeder or helping a dog in a need.
Please read those threads as they will help you understand the previous responses and help you make an informed decision.