I am looking for work of the Maharal on Rosh Hashana and hopefully Yom Kipur. can someone help me?
The Maharal doesn't have any book entirely dedicated to these two holidays, but his short Derasha for Shabbat Teshuva is about Yom Hakkippurim.
For more, you might also be able to look through his commentary to aggadot on relevant tractates. The Machon Yerushalayim edition of Maharal's books (some on Hebrewbooks.org) also have extensive indexes, so you might be able to find something there (for example, the entry for Rosh Hashshana in the index to Netsach Yisra'el).
From Wikipedia I see that he wrote a book called Shamayim Vaarets on Rosh Hashanah and Yom Kippur. But I don't know how to find it.