Brake Upgrade to 203mm disks

Upgrading the Homie to 203mm disks is not trivial, at least what the rear wheel is concerned.
For the front wheel the Shimano adapter SM-MA-F203P/P fits perfectly and the entire exercise is each.
For the rear wheel I have not found a fitting adapter.
I tried the Shimano SM-MA-F203P/PM is not high enough. There is still a gap which needs to be bridged with washers. I did this on my Homie - it works, sits firm - but is sort of a provisory solution.
Does anybody has experience with this?
A hint for a fitting adapter?
I found the PM-PM-F/R203 adapter. Have it on order.
I hope two of them will bridge the gap.
Any hint is most welcome.
I noticed Nireeka offers an upgrade kit.
So they must have identified and ship an adapter fitting the purpose.
Thanks!