In Klingon HISlaH is the answer to a yes/no question rather than an enthusiastic agreement. No question was asked, so I'd recommend teH! (it's true), Qochbe' (agreed) or tlhIngan maH!
KGT describes two slang words that can be used here:
The word chong vertical may also be used as an exclamation expressing approval or satisfaction, somewhat like standard maj (good).
chong literally means be vertical.
The word qu’ may also be used as an exclamation (Great! Wonderful!).
qu' literally means be fierce.
chong and qu' in their slang forms are said to be interchangeable.