On Saturday, June 8, 2019 at 7:44:37 PM UTC-7, John B. wrote:
On Sat, 8 Jun 2019 18:39:26 -0700 (PDT), Sir Ridesalot
wrote:

I need a 9-speed 14 teeth and a 9-speed 18 teeth cog for something I'm doing.
Does anyone make a 9-speed cassette with one or the other of these
cogs or even both of them?

Cheers

You can use something from a 10 speed cassette, at least I have added
a 32 tooth cog from a 9 speed cassette to a 10 speed cassette with no
problems.

Just from my experience, the cogs on 9 and 10 speed cassettes are
very close to the same thickness but the spacers between the cogs is
different so you need to use the correct spacers if you are using any
sort of indexed shifting.
--
cheers,

John B.

Cassettes are made all in a set is for a purpose. The shifting lifts are aligned properly for shifting. If you mix and match be ready to get noisy shifting.

I think that both of the gears you're looking for are on the normal 11-23 Shimano cassettes. But the 18 tooth I attached to a 16 tooth on the Ultegra cassette.