This is the webpage for the hobbies anual
W. Hobby Limited
The other odd place to look are pound shops - they have a lot of little LED lighting things, sort of like battery powered night lights etc. Some of these use coloured LED's and flash too, which would be useful for navigation lights, you'd just need to lever them open with a screwdriver and lengthen the wires as required.
Also on ebay sellers often sell LED kits for R/C cars, you could do a search and then ask if they could provide a set with the led's you need, maybe red, green for port and starboard, high intensity white led and some of the more natural white off white colour for the interior cabins.
I know there are also lighting kits available for Starship models, but you probably don't want warp nacelles on your 747!
If you have a flying stand for the aircraft you can also fit the switch and battery in the base and then run the wires up inside an aluminium tube or whatever to get the power to the model too. That'd save having to house the bits in the fuselage and problems getting to the battery compartment too.
Alan