I wouldn't at all consider trying to jerry rig a non-certified EFB into that role
So, you would prefer to
a) print out the plates for every possible diversion airfield along the route (say, 10kg of paper)
b) go flying with just the dep dest and alt and hope nothing unexpected crops up?
c) subscribe to, and carry, and regularly insert the updates into, the printed Jepp subscription?
Which?
I would always print out the expected stuff (like I've said) but a source of approach plates for the whole relevant area means the flight is MUCH safer than it would be otherwise.
The Jepp UK paper binder alone is huge. A European flight of say 800nm would involve carrying some 20kg of Jepp binders.
"Certified" means very little. Anybody can get a TSO for a piece of junk - just takes a lot of time and costs a bit of money. I've seen plenty of defective design avionics which is TSOd.