Free Download from Arsha Avinashi Foundation:
http://arshaavinash.in/index.php/books-on-sanskrit-grammar/
Printed versions are available at Amazon and CreateSpace
http://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=medha+michika
https://www.createspace.com/pub/simplesitesearch.search.do?sitesearch_query=medha+michika&sitesearch_type=STORE