Mine has been damaged for a while, but I could charge the tablet nevertheless, now it's very difficult to find the correct way to insert the plug and make a good contact.
I saw places online selling the complete back cover, but I just need the socket.
If I cannot find the correct one maybe I could do a hack job using one for a cell phone (I don't know where to get that either) and some loctite, though the tablet socket isn't soldered making the hack slightly more difficult.
I'd prefer the proper replacement part though.

Any _EU_ Nokia charger from past 2 years should work. They're compatible. I'm using one included with my (old) Nokia phone for my N810. It works well. Again, all EU.

In my understanding, he doesn't want a charger, he wants a socket for the charger to plug into.

Sending it to Nokia for service is the usual recourse; I don't know that anyone's successfully replaced one. Obviously, if you can't find the appropriate socket, there are any number of plausible alternatives; all inferior, though.

Exactly

I'd prefer to avoid that, it would be surely cheaper to buy the whole back cover.
It should be simple enough to change justt the socket (no soldering required) provided you find the part.
Considering how fragile the 2mm socket/plug are, I think it's difficult to find an inferior alternative

Update: it seems that the socket is ok (well almost, when the tablet fell I had to push a tiny amount of foam behind the negative pole with a needle, in order to make the plug fit snugly) since the car charger can charge just fine.
It's probably the plug, a cheap usb ca-100 knock off I used to replace the broken original plug (that worked for some months but it finally stopped working).
My frankenplug worked for a couple of weeks but it couldn't withstand the wear.
Or maybe it's the combination of a half-broken socket with a so and so quality plug.
It's worth noting that the car charger is also from dealextreme and it worked very well for a long time, but then I don't use it as much as the wall charger.

You know what? I inserted a couple strands of fine wire inside the hole (positive pole) of my frankenplug and it is charging again.
I don't think it'll last but it'll give me time to order a (different ) new one from dealextreme.

The socket is on the mainboard, not part of the case.
If it ever does go bad, I'd suggest getting someone (expert) to run a wire from the USB socket (+)ve to the charger (+) so you can charge off USB.
Just like Nokia SHOULD have designed it in the first place.

Nope, the socket is in the case and it just makes contact with 2 pads on the mainboard when you assemble it.
And I don't think what you propose is a good idea since the usb on the n800 can work as host (in fact I use it almost only in host mode), so it will be supplying its own 5v.

Good point. I think I'll just go hide in the corner now. :-(