Chase HQ II: Special Criminal Investigation was probably produced in very small amounts. Actually the existence of only two cartridges of this game was verified.
It has since been reviewed in Retro Gamer, and is believed there are only two copies in existence.
There has been lots of talk about this cartridge and even attempts to contact the author for transfer. But as of this date, nothing has come of it.
eBay sale
On 24th October 2010, a copy of Chase HQ II was sold on the auction web site eBay for a staggering £906.87 — by far the highest price that has been paid for a single Amstrad CPC game on eBay.
The auction was followed closely by CPC enthusiasts on the CPCWiki forum. As of January 2011, it is not known who won the auction.
- Photos from the eBay auction ending 24th October 2010
The case, cartridge and instruction manual 
Close-up of the cartridge and instruction manual
Video in Youtube
Recently (on 13-02-2012) a video appeared on YouTube, showing an unknown copy of Chase HQ II running!!
It is not clear to who this copy belongs. However, two things are certain: a) the 6128+ shown has an AZERTY keyboard (sold in France) and b) the computer is plugged into a UK type plug.