I also have the CTEK MXS 5.0 sean, great charger but tad pricey, the 3.6A one would do just fine. As has also been said lidl/aldi often have their version which is decent and cheap. I havnt seen any that just plug in to the accessory socket though, youd need to buy a male din plug and make up a connecting lead, dont butcher the charger.
You could get charger on by removing the plastic starter motor cover and clipping charger to the +ve terminal of the starter and ground to the frame. Ive never done it on the bike but plenty times on cars and it works, though you probably dont want to be using a beast of a car battery charger. My car charger has a 5a option and I would be happy to connect it to my bike in this way if i didnt have the CTEK.
To be honest though you should just get stuck in and get access to the battery terminals. Its not difficult and you dont need to remove the tank, just undo the bolt on the right hand side, the multiplug electrical connector beside the bolt, the 2 little tank breather/overflow pipes (these can just be popped off at the joiners on the right side beside the seat), fuel lines - yours is unlikely to have quick connects so have a couple of 8mm bolts to pop in to the lines from the tank once disconnected and lightly tighten down on them to stop fuel flow.the tank can be raised and propped up giving access to the battery terminals. Watch for the little ground wire, it should be long enough not to need disconnected but mind dont rip it. Dont think all tanks have these, but my plastic one does.
It sounds a lot but its really not, and good practise as at some point you may have to do it in the middle of nowhere at the side of a road in the pissing rain.
