There are situations where you need power supply, for example to take night shot with long exposure, here's a shot description who to fast and relatively cheap make power supply for Pentax camersa (K20D/K10D/K7) and perhaps other models as well. WARNING! I can't guarantee that everything here is correct and that it will not damage your camera, always double check everything. I make this device for myself and it works perfectly.
Alternatively you can buy cheap power supply for Canon CA-570 on eBay or any other auction service and mout Hirose connector.
Original power supply costs over 120 USD.
Power supply should give 8.3 V, maximal current: 2 A (basen on: this shop's site. As input power it's best to use power supplies used in laptops, they're compact and they can support high current and they're relatively cheap and voltage stabiliser. As voltage stabiliser I used L4960, it has wide input voltage, high current (2.5 A) and is relatively cheap. You can buy complete kit in AVT (AVT-1081) - costs 13 USD (without shipment), PCB itself costs less than 2 USD.
Schematics and PCB board can be found on page 9. of datasheet for L4960. Below is a part of this page, almost identical schematic is used in AVT kit (AVT-1081) mentioned above, I added resistor value for 8.3 V:
You must set output voltage to 8.3 V - for schematics above: R4 = 3 kΩ, for AVT-1081 kit: R3 = 3 kΩ. In case of AVT kit you must drill holes for radiator. Below is a picture with pinout for special plug (based on zdjęcia z flickr and self study):
After assembling AVT-1081 kit I powered it with 15 V and loaded with 1.8 A on 8.3 V side (lightbulb). Output voltage dropped to 8.1 V and after 15 minutes radiator was worm (you could still touch it without risk of burn). After connecting camera (Pentax K20D) it used about 0.3 - 0.4 A during normal operation. I also changed input voltage from 12 V to 15 V, voltage stabiliser still gave 8.3 V. Device worked perfectly during few hour test with long exposure.
Below few photos of power stabiliser and special plug: