you could try Remay cloth. it is a woven floating row cover used for crops. it is whote so will reflect rather than absorb the sun/heat and will let UVB and water thru. it dries very quickly so will not bog down. I use remay sleeves for rearing all my wild silk moths outside in summer. You can buy it by the roll. With wond, rain, etc. you would prbably have to replace it once a year or so. Here is a link. It may called something else in PR but this should get you started. Btw, nice cage 
this is about the company
www.reemay.com/applications/apli_agriculture.html
this one is a retailer. Not sure if they'll ship to PR but I am sure you could find somone who does or even a source locally.
Remay - retailer
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Chameleon Help & Resource Info
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