Loaded some CM yesterday. My Lyman dies are leaving a ring deformation around the tip of my ELD-X loads. Is there a source for an appropriate 6.5 seating stem?

No they do not.
But have you considered polishing the current stem with say something break the edge, and then polish with flitz?
Are you shooting compressed powder loads?
Are you cleaning your brass with ss pins or other wet methods?

Pics of the scarred boolits.

Switch to a Forster Ultra Micrometer seater; the standard stem will work with almost any bullet on the market, and the micrometer top makes seating depth adjustments easy.  The metallurgy and shape of the stem spreads the contact area to minimize bullet deformation.  The sliding sleeve (similar to a chamber) locates the case properly before the bullet enters the neck which reduces runout.

Something in your loading process is making your bullet seating force very high to get the sort of swaging your loads show.  What is the difference between the sized and loaded OD of your brass?  If it's more than a few thousandths of an inch, you may want to use a mandrel to set a more appropriate diameter.  Do you use a dry lube on the necks?  Is the as-fired coating left in the necks, or is the brass sparkling clean?

No sure if it was bullet construction or brass but the SSTs I loaded did not suffer the same deformities.

That takes the natural byproduct of firing the round which lubricates the case neck easing the seating of the bulllet
If you are the increased resistance in the case neck may be causing increased resistance when seating the bullet.

Did you chamfer and deburr the case mouth?

Is it a compressed load? Ive had that problem with compressed loads. I would get a different seater or try to polish the one you have. It's it's compressed enough it may not matter.