We’ve covered jigs for drilling perpendicular holes without a drill press here, here, and here. Though it may not be as versatile, Gladstone’s simple and elegant solution requires no assembly, and there are no parts to lose.
Gladstone makes their drill guide from hardened steel to last a lifetime. Looking somewhat like a miniature hockey puck with holes, it allows you to drill 1/8″, 3/16″, 1/4″, 5/16″, 3/8″, 7/16″, and 1/2″ holes accurately with just a hand drill. If you need an angled hole Gladstone recommends using a tapered “pillow” underneath the guide. Say you need to drill an 80° hole — you’d create a shim with a 10° taper.
You’ll pay $22 for Gladstone’s drill guide.