I use reading glasses.
I buy half a dozen pairs at once from Poundstretcher or similar, for usually £1.50 or £2.00 per pair. At that price it really doesn't matter much if they get broken or lost.
Then I keep a pair by my home deak, a pair by my main sitting chair, a pair by my beedside, a pair in the office, a pair in the car, and a pair in my man-bag.
That way, wherever I am, there is usually a pair handy.