I'm no expert but I recently bought one on fleabay. So I have looked into it a bit lately.
My take on it is, while many people say it's a hitch lock off a given model of camper etc, as in your post, what you actually need to know is the model of hitchhead that the lock will suit.
E.g. Someone could say this is a hitch lock off a pathfinder but I don't think that's important. What's important is the type of hitch head. E.g. Aks1300 or ak300 etc. Stabiliser or non stabiliser type and so on.
If buying new you can find out the model of lock and which hitch heads it suits. If buying 2nd hand most sellers probably won't know the model so what I did was send them pics of the hitch head I wanted it to fit and asked if there's was that type. Then many are down as collection only but it's actually no problem to post.
I was lucky enough to get one as new for small money. probably because of the above confusion. Mine is a bulldog. From what I've read hitch locks don't prevent theft, they just act as a very slight inconvenience to a thief and an insurance requirement in some cases.
So in short I think you need to confirm the hitch head you have.
Then confirm which locks will suit that.
Then decide if you're going new or used.
There may be one to suit in the classifieds on here and the sellers are likely to be more informed than some of those on general auction sites. Hope that helps rather than confuses!
If it is a standard non stabiliser hitch then any box type hitchlock £20 pr more will do. If you have Alko stabiliser hitch then as mentioned you need specific lock for hitch.
I went for a universal maypole hitchlock - it's worth remembering that a determined thief will get through anything - portable angle grinders are cheap and easy to carry. So (personally) I just worry about something that will keep the most casual thief away - and save my money for other stuff. I also don't lock my camper - as they can easily cut the canvas if they really want to get in - so why have them ruin it and cause all that damage - if they come in they'll quickly find I have nothing of value and leave!
I bought one of these.It fits up inside the ballhitch,and unlike most locks,this one cant be cut off.And it certainly wont come out without the key.Brilliant bit of kit.
http://www.ebay.co.uk/itm/UNIVERSAL-HITCHLOCK-CARAVAN-TRAILER-HITCH-COUPLING-TOW-BALL-LOCK-SECURITY-HIGH-/350755577146?hash=item51aaa95d3a:g:NUkAAOxyaFtR5v8I
Looks good and a bargain. I did get a wheel clamp too as mine was in a field for a long time, but not used it for a while and looked pretty terrible once it rusted. Again, was cheap and no doubt easy to break off even just with a crow bar, but stopped someone passing taking advantage