some devs here? How to contact them?

If you're okay with a female Knight character, maybe use the Yvonne avatar perhaps?
As an example, I used Yvonne (and the alternative color scheme to make her hands / gloves less 'sci-fi' looking), then I added the Viking-helmet prop to her head, moved that prop and re-sized it according to make it fit, and I think she sort of has a 'knight' look doing that (can save the prop settings for her too, then can quickly re-load it for another time when need be).

Here's an example image of Yvonne with the viking-helmet.
https://drive.google.com/open?id=1Pbv6sXoMP_yVsIwGyONy3VqgSrIFi5mO

If you go to the workshop and search for knight, there's a couple of results (though one is more 'cartoony' looking I think). I've not tried them though.

You might also be able to make a post about you're looking for someone to make a knight avatar for you, or find / commission someone there able to make a custom avatar for you at: https://gtm.you1.cn/app/274920/discussions/6/

There was one cool knight avatar for facerig, but I can't find it anymore. Oh, here it is:
https :// www . artstation. com/artwork/JlY6PD
Steam deleting links, just remove splashes.