Did exactly the same. This is the bottom crown race you need.
https://www.kineticbikebearings.com/fork-crown-bearing-race-1-5.html
One thing I did was drop the front travel to 170mm. I thought 180mm with the 38 would make it a bit too slack.
For anyone looking it seems like these options will fit:
https://www.kineticbikebearings.com/fork-crown-bearing-race-1-5.html
https://www.cannondalespares.com/Cannondale-Crown-Race-1.5in--45-Degree--K35108/product_detail/3-48566