One of the things I did when I only had one collet (5/8" in my case) was to machine split sleeves in different sizes to put smaller collets in.
Do you have a lathe?
You could chuck up a piece of 1" steel, drill undersize then bore to 1/2" (maybe about 1" deep). You know you have it right when a 1/2" end mill will go in, but you feel the air pressure, and it pops when you pull it out.
Then without removing the piece, turn the outside diameter to 3/4", leaving a small shoulder. The shoulder will prevent it from sliding into the collet.
Then slit the side. You can do that with a slitting saw, or if nothing else, a fine-toothed hacksaw blade.
Here are three commercially made ones (Hardinge) and the one I made. Mine has one slit and it surprisingly accurate. The Hardinge ones are split on opposite sides and from opposite ends (4 splits). You can sometimes pick them up cheap on ebay.
At least with a 3/4" collet, you have a lot of tooling that will fit in it.
Find a drill chuck with a straight-shank 3/4" arbor and cut off the arbor beyond where the collet will grab (makes it easier to install without having to relocate the work). That will give you drilling capability without having to have all the collets in the world.
You can pick up straight-shank end mill holders, but that will give you tool flex with the overhang, but the shank will be 3/4" so maybe not that bad.
Steve