I have modified both Meco's, the Gentech "Compact" torch ( big
brother to the Little Torch), as well as all our Hoke-style torches
to the hypodermic tips you speak of. I find they are far superior to
the slow to remove and adjust Little Torch tips, or the Meco and
Hoke's limited sized threaded tips.
Rio, or a number of other supply houses carry the hypo tip sets,
which come with a male-threaded adapter. I've found this adapter only
fits the Hoke torch, so you will have to weld or solder on the
adapter to the Compact or Meco torch neck. It takes a little work,
but having the quick-change tips in such a huge variety of sizes is a
big plus for me and my students.
I have these hypo tips in every size from nearly too-small-to-light,
up to a massive 3.4 mm. They all fit onto the adapter with a quick
quarter turn by hand. The thing is, the Gentech "Little Torch" and
"Compact" torch have fairly restrictive internal plumbing, so you
can't take advantage of the larger tip sizes to produce high heat as
you can with the Hoke or Meco, which have larger, more robust
plumbing inside. With the right tips, you can make a small flame with
a larger capacity torch body, but you can't push out a larger flame
with a restricted sized torch body. Or maybe you just have different
torches for different sized melting and soldering jobs.