Condoms falls in the category of "buy as needed" (grin)
I am surprised no one mentioned the UPS/FEDEX/DHL/USPS style of touring where you mail-ahead clothes and supplies to strategic places along your route, place what you don't need back in the box and send them home. You can go on like this for a very long time and it is a convenient way to get hard-to-source supplies in each country and your souvenirs back home. Not the cheapest way to go, but darn convenient. Done this before when traveling for business and it sure is sweet to not carry as much luggage.