Sorry I’m just now seeing this, and late to the party is just fine 😍 I’m looking at redesigning it this year anyways!
I’m not sure if this is similar to what you meant by an accordion covering, but what we did was design a mold that we 3D printed and poured silicone into to create a seal/cover that will stretch as the piston of the linear actuator slides in and out.
We actually did start out with an accordion/bellows design, but found that the flexibility of the material alone was more than sufficient to handle the required distance of travel on the actuator piston!