Are you trying to connect to 3 virtual machines or 3 ESXi host? If you're looking at 3 different hosts you might need to go with a USB over IP device.
With one host the maximum per VM is 20 so you should be able to get it to work with a USB hub. In this KB article you'll note that a 7 port USB hub is supported - http://kb.vmware.com/kb/1021345.
This would be a sample of a USB over IP device - https://www.digi.com/products/usb/anywhereusb. In the VMs you would install a USB driver which would simply redirect a virtual USB port over the network to the USB server. Nice thing is you can move the VMs between hosts without having to worry about USB connections.
You can also get a software option for this - http://www.incentivespro.com/products.html and I think there may be one or two open sources opens as well.