I'm by no means an expert in the Incas, but I think a good starting point for your search (just an educated guess) would be the Inti, considered to be some sort of "Sun God" - modern representations of it can apparently be found in the flags of Argentina and Uruguay. I'm guessing that probably there would be some sort of ancient representations of this entity, as well.

I've enjoyed reading the scholarly interpretations of Incan history by Nicholas Asheshov in the Peruvian Times. While not exactly providing an image of the sun, their buildings aligned with it. You might have seen this article on how Incan leaders demonstrated to the people that they could control the sun, as seen in their architecture. http://www.peruviantimes.com/10/the-people-who-ran-the-sun/23987/

I think early Spanish chronicles talk about physical representations of the sun, in the form of wacas, a sacred golden statue which had its own temple. 

"Much of Coricancha was filled with gold, with one chamber containing a giant sun disc, reflecting sunlight that illuminated the rest of the temple. The disc was aligned so that during the summer solstice it illuminated a sacred space where only the emperor himself was allowed to sit."  (from link below)

http://www.theguardian.com/cities/2015/mar/25/cusco-coricancha-temple-history-cities-50-buildings

Inca Gold Sun Mask

http://www.ancient.eu/image/2356/

Finally I found an article about Incan Rock Art, including several representations of the sun: http://www.rupestreweb.info/incacusco.html. That brings me to the question: Are these representations typical just for the Incas, or are they more of a Pan-Andean pattern?

Hi Stefan. Rainer Hostnig's article you quote is a great research, but his analysis of iconography is just one of many possible interpretations. There is no solid idea of the Inca iconography of the sun, not one single image. Garcilaso's description of the "sun disk" of Qorikancha is definitely a product of a confusion, that generated even more confusion later on. The most reliable information available is that about Punchao, the statue (clearly in the form of a human figure) that was kept at Qorikancha, later was taken by Manco to Vilcabamba, then ended up in the hands of the Viceroy Toledo and finally was sent to the Spanish court. But there are only written descriptions of it, no images. There are several important articles written on the subject.