Ok, I spent *far* too long while I was supposed to be working trying to find a shop vac type canister vac that looked like that droid. Focused on ones available in England easily. This one seems like a good match (20L Wickes Wet/Dry Vacuum/Blower).
https://www.youtube.com/watch?v=S_fRJStKCu0
And some annotations:
The center hose attachment (red) is a "duh". That sort of mostly confirms that it's a shop vac of some sort. You could get that other ways, but really?
The hose on the left is also pretty clearly a vacuum hose. They could've used such a hose without using the vacuum itself, but model makers tend to use the parts at hand. So if one looks like a hose and the other looks like the canister it increases the odds that both are what they seem.
There's also a seam between the blue and black parts of the vacuum, which is readily apparent on the right (upper green arror on right). But again, many vacs of this type have a seam in that area.
The top green arrow whos the top of the body of the vac. It's pretty clear they did something else for the upper part as the mechanism is much too large for that droid's upper portion - however it's also clear that the cap of the droid's body also can't be tall enough for *any* shop vac's fan, it's not bulky enough. There may be other vacs with that proportion.
The "weathering" painting on the droid makes it hard to tell, but the body's pretty flat.
What I find really compelling is the feet. This shop vac has unique corners with a recessed round part above the casters and a pair of triangular supports above them (green circle). I haven't found any other vacs with corners like those. (I thought mine at home was similar, but it differs as well). This is what really makes me think this model is it.
I also noted the yellow arrow where the hose connects. It's pretty blurry, but this model hose goes inside the plastic connector, which has a stepped fitting, very much like that. There's a clip on the real hose though that would have to be on the back side or removed.
So... like the Mythical Monster Mouse Droid this seems to be one of those reoccurring patterns where the droid builders are trying to build a bot, so they look around the shop for things at hand. In the evening when the cleaning staff comes in, they look around in confusion, "where the )(@*& has my vacuum gone?!?!?" (or in the mouse droid's case, the tip cart).