I was recommended to this agency in Causeway Bay: New Famous Employment agency
http://www.indo-maid.com.hk/ and found my Indon maid through there. This agency is owned by an Indon Chinese lady. You need to speak Cantonese to deal with her and her staff. They were efficient and charged reasonable fees, and are accredited to submit papers to the Indon Consulate.
To find a good maid you have to ask all the tough questions at interview time. This is still not a guarantee, as you will have to supervise your maid well when she comes to work for you - same as any worker a company hires. Thjere are many threads in this website on this.
With Indon maids the majority of them are muslims and you must be culturally sensitive. Muslims do not eat pork. I have heard of HK Chinese families forcing the maids to eat pork. It is appreciated if you are aware of the Muslim religious customs - eg during the fasting month (Ramadhan) I tell my maid to do lighter duties and I give her her bonus ahead of the Muslim New Year instead of Christmas.
Some Indon helpers come from rural areas. The less educated they are, the more superstitious they may be and believe in black magic. When you read in the press of Indon helpers doing bizarre things like lacing employers food with urine or menstrual blood, this could be because the employers have mistreated them and the worker is taking revenge in some sort of black magic tactics.
It is hard to make generalizations, but be fair to your employee and she can be loyal and good-natured in return.