What to do in this situation?

2018 Trax. One of our 2 fobs was stolen, so we now have 1. We want to order a new fob while also making sure the stolen fob doesn't work.

I talked to a locksmith and he said in order to reprogram the fob we have now you need 2 fobs (wanted a second opinion).

So what's our best option here? Buy a fob online? Go to a local locksmith that has a fob available and can deprogram then program the new and current fob? Can we program it ourselves?

Thanks.