What about a Garra, they eat predominantly algae. The Panda Garra could readily be mistaken for panda cory's in all but size.
PANDA GARRA
Latin Name: Garra Flavatra .
pH: 6.5-7.5 .
Adult Size: 6-8cm .
Minimum Tank size: 75 litre .
Something different..
I wouldnt put a group of Flavatra in a 75 litre tank tbh, much too small. My opion, given that they should be in a small group of 4 or more, and grow to 4" each.
I also have to say, have you ever seens Corydoras Panda? They look nothing alike, again, in my opinion. Completely the wrong colour and shape?!?! Large fat brown fish, verses small delicate pink/white/black?!?!
In response to the OP, there are very few fish that exclusively eat algae. You could try otto's, but once the algae is all gone, they'll need something else. DONT let anyone tell you to buy Chinese Algae eaters wihtout prior research either. They are commonly sold as a solution to algae, but will infact grown much larger and develop a taste for other fish's slimecoats and eyes.
Its common practice to advise those looking to deal with an issue in the tank, to deal with it themselves. Not good practice to introduce something to the tank to deal with a problem you can fix yourself.
If your having probelms with algae, try looking at ways to stop the cause. Excess light, too close to a window letting in sunlight, overfeeding, etc.
Hope this helps.