Go to your local hobby store and purchase a little bottle of Testors model paint in the color you need. Get yourself a model paint brush and brush cleaner too. Then after you've cleaned and dried your clubs, paint the numbers and lettering back on the clubs. Don't worry about being neat as the numbers and lettering are recessed. Just get the paint in the recesses but don't overdo it. Let it dry for about a half hour or so, then using a scotch brite pad dipped in soapy water, gently rub across the numbers and letters to remove the excess paint surrounding the recesses. Wipe dry and your done until they need it the next time. 

Just wanted to say thanks for the question and the reply.  Have been wondering about that myself.