I ended up buying this one, which was a great fit for the phone in its dual screen case: https://www.amazon.com/dp/B07VWV8LDH/ref=cm_sw_r_cp_apa_i_vvutFbXBTTJRR

That link shows a pic of two phones inserted in the pouch. From the looks of it they seem to be an iPhone, either a 8, 8 plus, 7 or 7 plus since they have those big upper and lower bezels. So let's see if a V60 with dual attachments will fit using their dimensions.
the iPhone 7 is 7.1mm thick x 2 = 14.1mm.
the iPhone 7 Plus and 8 are 7.3mm thick x 2 = 14.6mm
the iPhone 8 plus is is 7.5mm thick x 2 = 15mm

The Dual Screen Attachment is 14.9mm thick (0.586") by 175.9mm (6.9") long, by 86mm (3.38") thick. So I would assume it would fit that case if the two phones in the picture were a iPhone 8 plus. If they are a iPhone 7 plus or 8, it might be tight. if the phones are a iPhone 7, I don't think there will be enough space for the V60 with dual screen attachment. But the only way to be absolutely sure is asking the manufacturer / seller to see if they can tell us what the internal dimensions of the pouch are. I left them a question. let's see if they reply in that amazon page.

But in searching for an answer to this topic, I came across this one on Amazon that would be big enough. It states inner dimensions to be 6.94" (176.3mm) long by 3.95" (100.3mm) wide by 0.67" (17mm) deep.
There are quite a few other ones in Amazon, just search "V60 extra large phone holster" and then go by the dimensions I posted above.