I think you are out of luck for Shimano or Sram. (edit--that's interesting to combine the two cassettes. And you would get the 18 cog!)

I think it's a marketing decision to not offer 13-28 or 13-29 on Shimano. It would be very useful for a lot of riders. And the new wide range cassettes are often 11-30 or 11-32. The 11 is totally useless, and there's big speed gaps between shifts.

I have a Campagnolo 10-speed drive train. So I can get a 13-29 cog set. It's not supposed to work with a short cage derailleur, but it's fine on many bikes.
The only time I miss having a 50-12 high gear is on medium grade downhills, where I want to pedal to increase my speed past 32-33 mph. I start spinning out the 50-13 at about that speed. That's very rare--coasting downhill is fine for me at that speed.

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I was using a 13-26 cassette. It has an 18 cog, which I liked a lot. I'm pushing hard if I'm at 18-20 mph, so it was great to have 1 mph jumps between shifts. I could get the exact cadence I wanted.

At 90 rpm:
50-19 is 18.5 mph
50-18 is 19.5 mph
50-17 is 20.6 mph.

But I've kept the 13-29 on the bike, since I use the 34-29 low gear a lot on hills over 7-8%. And I'll even use it on 4-5% grades to spin up at 95 rpm.

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The Shimano 12-25 10 speed is:
12 13 14 15 16 17 19 21 23 25
Shimano 12-27 10 speed. The same except the two lowest gears.
12 13 14 15 16 17 19 21 24 27

Campagnolo 13-26 10 speed:
13 14 15 16 17 18 19 21 23 26
Campagnolo 13-29 10 speed. It drops the 18 cog and adds a 29 cog.
13 14 15 16 17 19 21 23 26 29