For me plastic squishy bottle. You can still get them from OCP or eBay. Also a seller from Taiwan sells some with a screw in cal in the pipe tube.
For me the best bottle is a Snoop Leak Detector Fluid bottle. Holds 8oz, fuel-tight cap, industrial/workshop quality, and has a tube that can be pulled out 10" if required and still remain usable! Buy a bottle and tip out the soapy water or ask at a local engineering/HVAC shop, they may use it I use it for all the "awkward" lamps, from Primuses to Vapalux (thread tube up through a bottom hole), and stoves where the priming dish is down in the guts of the unit and difficult to access, etc. Alec.
I had a short length of 3/16" copper tubing laying around in the shed so I bent it to shape and stuck it in the cap of a washing-up liquid bottle, I've been using it for years now and there are very few lanterns on which it doesn't quite work, e.g. Coleman 235. I had to drill out the hole in the cap to accomodate the 3/16" tube but a smaller tube e.g. 4mm will work just as well.