Where can i get oak trim?

You can bend vinyl trim that tight by applying a little heat, but you won't be able to bend a solid oak trim piece that tight.

You've got a few choices:

Make a trim ring from a solid piece of oversized lumber (wouldn't be my first choice)

Make trim by gluing sections of wood together end to end (mitered), and then cut off excess corners, and run a router around it. (This method makes it very visible, where you've glued the different sections together)

Or - and this would be my choice, Make a form that matches the post. Cut thin strips of oak (for a 6 inch diameter - that's a 3 inch radius - so I would make the strips less than 1/8 inch thick). Now clamp the strips around the form, gluing between each layer as you go. Finally, use a router to create the profile. This will provide a trim that is custom fitted, and yet looks like a solid piece of oak, that is curved to fit the application. The several thin strips will look like the natural wood grain. It's a bit more work involved, but will produce the best looking results. I've used this method to create bent trim of all sizes for a number of custom products.

Have Fun

difficult issue. seek with a search engine. that could actually help!