One of the users mentioned Gita Press, which is a good translation. Here is the link:
http://book.gitapress.org/product-category/topic/ramayan/
Another is by Parimal Publication, Delhi. Here is the link:
http://www.parimalpublication.com/index.php?route=product/product&path=7&product_id=218
Rajaji's version is an abridged one. It is good, but it skips some details for a well intended reason (to make it readable by all groups of people including a middle school kid).
Also there is an English translation by Smt. Kamala Subramaniam published by Bharatiya Vidya Bhavan.
https://www.amazon.com/Ramayana-Kamala-Subramaniam/dp/8172764324
But keep in mind that this is also an abridged version, albeit larger than Rajaji's one.
And there are many versions on the Internet like other users pointed out.