Probably should try a Hotel and Restaurant Supply store...sure there must be some in SD. There's one 1/2 way between Bavaro and Veron on the right side as you're going east.
I used to see a place for estantes on Romulo betancourt, between nunez de Caceres and Privada or maybe it was on Sarasota, don't recall the name though. But these are business for retail stores and warehouses.
If being used for electronics, you might consider shelving made of a material that doesn't conduct electricity unless you are absolutely sure your electrical system is up to code. Non-isolated equipment sharing a metal stand, fry one, potentially fry them all.
I know this is old school, But cinder blocks and 12" boards. don't conduct elect. and you can make it as long or narrow and as high as you want and may be cheaper and easier to get. Just a thought. We used them all the time in dorms in college.
Metropolitan Wire from Wilkes-Barre PA is a leading supplier of industrial metal shelving. It is plastic coated so should alleviate concerns about conductivity. My MIL used to work for them. Searched for RD suppliers using this - http://www.metro.com/howtobuy. It gave me phone numbers with a 561 area code?
You could try contacting them to see if there is a distributor in RD.