You also may be able to find a LED centering ring (gasket/ adapter ?) of the correct size. Or at least close. Match the LED size for the inner hole and the reflector hole for the OD of the gasket. These are sold at several places, but the Convoy store on AliExpress has a decent selection. They help with setting the reflector height and centering. Also for insulating the reflector form the MCPCB. I think a good idea when using any reflector. They are also very cheap.
Some info here:
An example, you will need to search or look for the size that you need.
https://convoy.aliexpress.com/store/1100591265/search?SearchText=+gasket
Or find something close and cut or mod it to fit. You also may be able to find someone to 3D print one for you.