It's called a surat keterangan catatan kepolisian.
I got mine from the Police office in Denpasar. They tried to charge me an unofficial 200,000 Rp for it but I got it for free after refusing to pay for it.
If you are a foreigner I don't think you can get one if you don't have a KITAS but I'm not 100% sure about this.
Their phone number is 0361 243 500 (Indo language only most likely) and the office I am talking about is in Jl WR Supratman (next to the mosque).
I'm just guessing here but wouldn't it be easier to get one of these from your Embassy?