Paper Source, Download & Print, and Zazzle have online templates for RSVP cards, as of 2015. Many have corresponding invitation or reception cards available, and some templates are available for free.
Paper Source has templates that can be opened in Microsoft Word with several sizes available. The company provides basic fonts that users can change in Word, as well as ink colors that match the colors of the invitations.
Zazzle and Download & Print have templates available at a cost. Download & Print has 101 RSVP cards available as of 2015, most costing $9. Zazzle has 256,765 templates available. Most of the templates are customizable, and many of them cost under $5.