This power supply is powerfull and easy to make. I've been using it for a while and i'm very satisfied. It can produce 5A at 30V. All of the parts are available on ebay.

Step 1: Part List

http://www.ebay.com/itm/DP-30V-5A-Constant-Voltage... DC-DC power supply modul

http://www.ebay.com/itm/10Pcs-4mm-Banana-Female-Ja... Banana connectors

http://www.ebay.com/itm/AC-DC-Inverter-Module-110V... AC-DC converter

http://www.ebay.com/itm/10Pcs-Panel-Mount-Screw-Ca... Fuse holder

http://www.ebay.com/itm/IEC-3-Pin-Chassis-Panel-Mo... IEC C14 connector

http://www.ebay.com/itm/Rocker-switch-rocker-switc... ON/OFF Switch

http://www.ebay.com/itm/Half-shells-Casing-Euro-Bo... Plastic housing

Step 2: Housing

When you have all the parts, you can decide their posision on the housing. The easiest way to cut big and sqare holes in the plastic housing is to drill small holes realy close so you get a sqare lined with small holes, than you just push out the sqare and grind the edges.

If you use plastic housing you don't need to ground the housing, but if you use a metal housing you have to connect the middle pin of AC connector (ground pin) to housing for your safty.