I would get a carpenter/handyman to make one for you. I had wooden thresholds upstairs and on the stairs from the carpet suppliers and they were ridiculously expensive. It wouldn’t take look for a handyman to make it up and fit it for you. Alternatively, there seem to be a lot of suppliers online who have them for sale.

Are the two floors exactly the same height?

(this is the third time of trying to post this - please Houzz sort it out)

When we had our kitchen done, we had our builder (one of whom is a trained carpenter) create an oak threshold to join the kitchen floor (LVT) to the (carpeted) sitting room floor, which were at different levels.

In the photo, the real oak is a slightly different colour to the LVT, but in real life there isn't a great deal of difference. I think it's looks pretty good considering what they had to overcome.

A competent carpenter/builder should be able to help you with a similar wooden threshold.

Agree entirely.