Did you try "Ferrari Genuine" ? they have apparently some indoor car cover. The car cover for the 488 should fit (my 488 came new with a "458VS" cover) if there is no Speciale cover, but you need a cover without vehicle name in this case. I do not know if a 458 Italia cover would be OK for a Speciale.
You can buy them off Ebay, dealer, Scuderia Parts etc. 458 Italia will work for the Speciale. Car dimensions are exactly the same.
These are recommended here in the UK - decent quality. https://www.classicadditions.com/en-GB/ferrari-458--car-covers/vml_1052-167234
I'm not sure if shipping from the US will make this unattractive, but quality and fit are excellent. https://coverking.com/#
