I need to replace about 20' of crown molding in my kitchen. It is a very common style in an impossible to find size. It appears to be 1/4 of an inch bigger than anything I can find. That extra width is in the middle of the molding so the ridges /valleys that run the length are slightly further apart than on the closest available size, so I can't even make it work with a little extra caulk at the top or bottom. I have taken samples to Lowe's, HD, McCoy's and Cassidy Jones but they can't match it. I really don't want to have to rip the rest of it down and redo the whole room as it has lots of corners and obtuse angles to deal with. Any suggestions of where I can look?

https://www.thisoldhouse.com/how-to/how-to-duplicate-custom-molding

In all seriousness, if its not in the Smoot Mouldings Catalog:

https://bmc.a.bigcontent.io/v1/static/BMC_Smoot_Moulding_Catalog_2019/.pdf

Then you should be able to go to a mill worker or a Millwork Shop and they can get a new cutter blade made, yes it's expensive, probably more than you will spend on buying and replacing with new similar.

HD or any of the big box stores are not where you need to go, you should go to a high end mill work shop.

https://www.bldr.com/location_college-station-lumber

I picked up high end base boards here. I was impressed with the selection.

As vitruvian said, call these people... BMC

If you're in Houston give Houston hardwoods a try. They were able to match some trim i couldn't find anywhere else.

Thanks for the advice, however, it looks like I am probably going to just have to redo it all.