This would be pretty difficult. A pair of computer glasses is made to accommodate your vision at approximately 24 to 30 inches of distance from your eyes. Unless you tend to hold reading materials at a complete arms length from yourself, this is pretty uncomfortable.
The best is to go to your doctor and get a reading prescription. If you want to go quick and on the cheap, find out what the power is of the lenses you use. If you have a written prescription for computer glasses, whatever the prescription is (example (+1.00 SPH), find a pair of drugstore readers that are about twice that (+2.00).
If you want to go the cheap and quick route for reading glasses, just bring something with small print with you to your local Walgreens, or other superstore, and try on all of their reading glasses powers (labeled on each pair) while trying to read what you brought at a normal reading distance.