Hi TNR, welcome to Yorkie Talk and sorry to hear about Sas.
I used the loop that attaches to the arm of a grooming pole, it's about 18" long. The end with the clip was attached to her harness, and he end with the adjustable loop went around my wrist (if she was in my lap or beside me on the couch), or my ankle or table/chair leg (if she wanted to be in one of her beds on the floor).
LadyJane clipped one of hers into a stroller to successfully confine the pup during recovery, so that is something else you might want to consider.
You are really not going to have to worry as much about keeping Sas under control during the first couple of weeks post-op. They simply don't feel like doing much, and it is pretty easy to keep them confined during that time. They also get used to having to be on-leash every time they go outside or being tethered to something indoors, so when they do feel like doing more (and shouldn't be allowed), they've become used to "the rules." They sleep and relax a lot during normal times anyway, but there
will be "moments" where they are restless and difficult. The results are worth it in the end.
It's important to think about what Sas's triggers are and what makes her react (jump up or down, run, get excited, etc) and eliminate those if at all possible. For us, a knock or doorbell makes Jez bolt to the front door, so we put a sign on the front door requesting no knocking or ringing the doorbell. It worked, several packages were left during that time without ringing / knocking and neighbors would call before coming over. At that time she never reacted to seeing birds outside but now when she sees them she goes into full terrier mode, so if we had to do this again today we would have to keep our blinds closed. And it helps a lot when they get to take their rehab walks.