I've been looking for something more suitable than this:
or the notorious funnel for filling paraffin lamps and stove. Hence the question. However the only UK suppliers for 1000ml wash bottles are a bit posh asking for 30 quid and more. Guess I'll have to buy one elsewhere!
I use a poly bottle that used to have some form of kitchen cleaner in it. You may know the type, green with a small red pop up nozzle you pick out with a finger nail.
It fills a lantern quite well but does need to be stored upright. Main advantage is that it is free, disadvantage you have to figure out how to get the stuff from the gallon bottle without fuss and spillage.
Go into halfords and you will find lots of bottles similar to these full of a thicker oil. I use one for topping up the oil on my motorbike cause I was always spilling it.
I use one of these for meths for preheating my taylor's stove: trangia fuel bottles
bit more money that the squidgy one but robust and safe for meths. guess it's not quite so crucial for paraffin. I've found you have to keep the things you're after upright as well, which is easier said than done on a boat!