I bought the UJK Drill Guide after toying with the idea of the Bosch PBD40, as mentioned by Nelsun. However, almost every time I’ve gone to use it, what I’m really in need of is a pillar drill. The fact that it’s portable hasn’t really come into its own either.
On reflection, I do not need the variable angle + the degree markings are a bit crude and there is no positive stop for zero degrees!
Also, unless you plan on using a decent 12v drill/driver, which is nice and lightweight, then any 18v drill/driver with a 4.0ah batt, for example, is going to topple over every day of the week.
If I was going to buy similar again, then I would get the DrillPro upgraded rigid Wood Peckers knock-off from Banggood, for £85. I have bought over a dozen times from Banggood, and while it takes weeks to ship, I have been happy with everything purchased (t-rules, rail clamps, jigs etc), as machining and materials have always been more than satisfactory.