Your riser's are fixed arent they ?
Eg they can't be loosened and moved forward or back ?
Might be hard to find, as the bolt pattern where they mount to the fork's is smaller than the top cap bolt pattern
Another option if you're good at diy, might be to take your's off and cut them 50mm shorter?
Then file them up square and deburr them.
You might have to drill and tap the thread's a bit deeper and run some shorter bolt's though