This is the awl I use for fine work and for round closing 2–2.5mm thick leather. It was made from a small allen key, though 3mm music wire would also work well. I cut the angle off the allen key, stuck it in a drill and tapered it with a sanding drum on a dremel while it was spinning. The blade is straight, as is appropriate for a medieval awl.
The tip is a fine chisel point about 0.8mm wide. The point was made by just rubbing the tip on a fine abrasive until it was the right shape. The awl blade maxes out at about 1.7mm in diameter at the widest part that usually goes through a closing seam.
Using this awl I can achieve 2mm stitches/12spi in 2mm leather without too much trouble, and with practice and concentration I can do 1.6mm stitches/15spi. The seam below was sewn at with 2mm stitches.