A 7-Speed would have narrower spacing and would not index with a 6-Speed shifter.
You should be able to find a used or NOS vintage 6-Speed that has bigger than 24.
Shimano and Sunrace still make new freewheels but I can’t recommend the Shimano. I don’t think the modern ones are as well made as older Sachs, Suntour, Regina and so on. I had one start to misbehave after at most 1000 miles.
IRD is making new free wheels in 5,6 and 7 speed versions. They cost a good bit more, but seem to be better made. And they supply replacement parts. They have 6 speed models that go up to 24, 26, 28 and 32. The jump on the 32 is from 24 which is a lot.
Anyway, here is the link:
https://www.interlocracing.com/shop/...arch=freewheel
Hope that helps.
Otto