Your best bet would be with an aid organization or NGO. If you are a resident of the US or EU, keep in mind that you can avoid paying for an expensive residency permit simply by declaring yourself a tourist upon arrival and then traveling outside of Rwanda once every 90 days for the length of your day. Your 90-day tourist visa automatically granted upon entry will be renewed each time you leave and reenter the country and it's a convenient excuse to go on vacation!.
Take a trip to a craft centre, like the Dancing Pots Craft Centre or the Cards for Africa workshop and sales room in Kigali.