Mercadolibre always has a lot of monitor stands advertised, although they're mostly wall-mounts, if that will work. (look for "soporte monitor"). You can also post questions to the vendors to see if they have such a thing. Maybe you could use a pair of wall mounts?
If you visit the various electronics and computer stores around Paraná and Sarmiento, you may find it. Ask the salesmen where you might find what you need. Maybe carry a picture or a sketch of what you're looking for.
Finally, a while ago when I was looking for an articulated arm to wall-mount a small LCD TV, I finally found it through a dealer on MercadoLibre who sells a wide variety of supports from an apartment in Belgrano. Try him at gusmancini @ arnet.com.ar.