Here is another maker of chassis braces for the Micra. Okuyama makes a few braces that can tighten up the chassis for you.
Here is a list of their parts:
Part Description Part Number K13 Strut Tower BAR/Steel/Front/TypeI 611 154 0 K13 Strut Tower BAR/Aluminum/Front/TypeI 621 154 0 K13 Frame Brace/Front 693 154 0 K13 Frame Brace/Center 694 154 0
Strut Tower BAR
Frame Brace/Front
Frame Brace/Center