RTD Vapors has some nice needle tip bottles (in addition to being a great source for AW IMR batteries).
30ml Luer Lock Bottle - RTD vapor
There are varying sized bottles that will accept varying sizes needles like this one..
18g Stainless Steel Luer Lock Needle - RTD vapor
I know the 16 gauge is a little too fat for the kayfun fill hole so the 18 gauge is best. Your application may be different. HHV sells needle tipped bottles but the needles are very small and requires a ton of pressure. Tough on the Arthur Ritis.
I have two of those 30 ml bottles from RTD. They work great. Soft plastic bottles. Noticeably softer plastic than the HHV bottles, but not flimsy. I use them with 18 gauge plastic needle tips. Good combo.
I also have 8 of the HHV needle tips. I like them for rda's, but they are a lot harder to dispense from than the RTD ones.