[Cieran]

Does anything like this exist?

 

[CaveManta]

Do you mean like this?

They are a Koss KSC75, modified to have earcups, which sit on top of the ear. And the headphone is open-back.

 

[Cieran]

Yeah I guess although I was kinda hoping for something a bit more sturdy and bigger if possible.

Presumably I could do the same sort of mod with my px100's? Where would I get those sort of cups from?

 

[musicisthekey]

That looks like a really cool KSC75 mod. I should look into it since I use these headphones almost every day.

 

[CaveManta]

If you go to this thread:
http://www.head-fi.org/t/433318/shootout-100-portable-headphones-reviewed-fischer-audio-oldskool-70-and-oldskool-rpm-33-1-3-added-03-01-12
And look for the modded KSC75 (Which is item "B1"), it lists what is used in the mod. It appears that the Sennheiser PX 200 leatherette earpads were put on them.
Because they are from a Sennheiser PX model, you should be able to use those earpads with the PX 100. But I'm not 100% sure whether they use earpads of the same diameter or not.
It is worth a try though, eh?