I have some powered USB risers I used for a few months. How many you need?
10 to 50 depending on their location and price.
You should check us out
We have risers and dual PSU adapters in stock and ready to ship from our California warehouse.
https://www.hashratestore.com/
I have bought risers from them, I can vouch that they are legit and offer really good risers for a fair price.