Use your brain instead. It's the best electronic calculator of them all, it keeps your eyes out of the cockpit and even better, it's free!
Calculate max drift from the formula:
max drift = (Wind speed in knots)/(airspeed in nautical miles per minute)
Apply it by using the (analogue) clock code:
Calculate the number of degrees off track the wind is, look at the same number of minutes on a clock face and use that as a factor of the full clock face to work out the amount of drift to apply.
i.e 30 degrees off=30 minutes=1/2 the clock face, so use half the max drift.
40 degrees off is 2/3 the clock face, so multiply the max drift by 2/3.
Full example:
wind 260deg/35 knots
TAS: 90 kts
Track required 305 deg.
Max drift =35/1.5*=70/3= 23 degrees approx. (*if the sum is difficult, multiply it up until it isn't)
305 - 260 = 45 deg = 45 mins=3/4 of the clockface.
23 x 3/4 = approx 17deg
therefore heading is: 305 - 17 = 288 deg. (my whiz-wheel gave 289 deg, which can't be bad!)
With practice it can be done quickly, even in flight, and the method will be as accurate as a light aircraft can be flown.
Note that the method does fall down for angles from 60 deg upwards (all give a factor of 1), but it'll never be more than 10% or so wrong, or just a few degrees in practice.