No reason why you can't buy team kit if you don't support the team. Like the look,like the brand, have an affiliation to it for some other reason...
I have a penchant for buy old Wilier team tops: old Cofidis, Brescia,Gerolsteiner because they were Wilier tops and I prefer retro/vintage to modern.
On a practical note, you can plenty of copies from Aliexpress (affiliated to Alibaba but the money goes into escrow until the goods are received apparently) - they're cheap as chips and plenty of choice; but I've found the body tends to be quite short, so the back pockets are higher on your back, and the pockets thenselves are shallow.
I only wear mine on the wattbike where I don't need the pockets - wouldn't want to risk losing anything out in the road.