There are some drug stores which sell an alcoholic solution of crystal violet (aka methyl violet) using the name "Gentian Violet." These come in small bottles, about one half ounce, and are sometimes mixed with 10 percent alcohol. They are already measured into a concentration of one percent or two percent, that is 1 to 100 or 2 to 100. A half ml of the one percent solution in a liter of water/alcohol would reach a concentration of about 1:20,000. Simply observing the shade of that concentration would give you a reasonably accurate idea of what 1:20,000 looks like and you could try to match it using an eye dropper. The risk in these dyes is using too much. Interested to see how it works out--good luck!