In my experience, (I had something similar on my T595), they're fixed using double-sided tape. I'd recommend backing that up with silicon adhesive and clamping it against the swinging arm overnight to ensure a secure and tight fit.
That design looks like a shell, which just fits over the outer face of the swinging arm so you shouldn't need to disturb the chain.
If Santa brings you one don't forget to post up some pics!
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