No one sells it.
SAE and Metric sets always double some and miss others.
Here is a list. SAE is generally cheaper than Metric for some reason.

4mm
5mm
7/32" (5.5mm option)
1/4"
6mm
9/32" (7mm)
5/16" (8mm)
3/8"
10mm
7/16" (11mm-slight variance)
12mm (edit: almost forgot the 12mm- d'oh. 1/2" and 12mm look close in print. No interchange.
1/2"
13mm
14mm
9/16"
19/64" (I bought that once for my '72 Ford. It's a 15mm)
15mm (cause it's always included, see 19/64")
5/8"= (16mm)
17mm
11/16" (rare now, use in a pinch on 17mm)
18mm (a must-have, use in a pinch on 11/16th)
3/4"=19mm
20mm (flare nut for fuel filters on GM)
13/16" (is the one I use)
7/8"=22mm (esp good for o2 sensors)
15/16'=24mm
25mm?

Sockets
1"=25.4mm (26mm works)
1 3/16'~30mm
1 1/4"~32mm

I haven't worked the rest out. This is mostly all from brain stem, but 25.4mm = 1" is good.