Focusing Targets?

Anyone aware of inexpensive easy to carry focusing targets. Problem is
my right eye goes in and out during the day. I'm using a D-50
currently that has an adjustable diopter in the eyepiece and I oftten
use a 2X magnifier: two variables that must often be reset during
different times of the day as my eye goes wonky. Looking for something
that is easy to setup and could help me get things into adjustment
rapidly. I'm using auto-focus more and more frequently but it doesn't
really do the job I want on anything over 50mm. Changeable focus
screens looks to be something to think about on any future bodies, miss
my Fs in that respect. Thanks in advance.