Headphones Volume Limiter hardware, to stop overly loud sound damaging my ears ?

There are such devices, but I think I'd go with a headphone amplifier that has built-in limiting instead. It'll be about the same price, and you might find that the headphones perform better than with the amp included in your audio interface. Plus you can get one that has multiple outputs, which is handy when you're recording or collaborating with someone else.
 
Limiters, surprisingly, are not standard features on headphone amps. But they are pretty standard in headphone amps intended for in-ear monitors (IEMs), so that's where you'll want to look. Here's one I haven't used myself, but it's cheap (single channel). I don't know if you can adjust its limiter. But if you order it from Sweetwater and it doesn't suit your needs, you can return it. They're very good about that. 

I'm in the habit of removing my headphones between listenings. I just drop them to my shoulders and then start clicking around... and yes, because you can blow your ears out. 
40 years in audio has taught me to never turn anything on at full volume, Keep those levels down until you need them and turn them back down before pushing buttons or plugging things in or out. 
 
so save yourself some money and use common sense.