Duvet Clip

I have a weighted blanket that shifts around in the duvet despite being tied to the corners. This weighted blanket has securing loops on its edges, but the duvet I use doesn't. I can't find another duvet of the same material with these edge strings, nor am I skilled enough to sew them on myself. Duvet clips don’t seem to be strong enough to secure the weighted blanket in place either, so I that's how this model came to be. The inner fitting is meant to affix to the weighted blanket's securing loops and the outer fitting should have just enough leeway to slide over it after the duvet is installed.