What Thunderbolt to USB 3.0 cables/adapters exist for OS X and Mac hardware?

I have the Late 2013 Macbook Pro, which has two USB 3.0 ports and two Thunderbolt 2 ports. I currently use both USB 3.0 ports and one TB2 port. I want to connect a third USB 3.0 device to the machine, but I don't want to use a USB splitter on one USB port as I'm concerned the devices would draw too much power from the bus. I have no current use for the second TB2 port and I would love to be able to use it for this purpose.

Browsing extensively online, I've found numerous docks, such as Belkin's Thunderbolt Express, that connect via a Thunderbolt cable. This would work, but it's an expensive, 'bulkier' solution (and not the one I'm looking for).

I'm aware that a USB 3.0 device wouldn't be able to take advantage of Thunderbolt's I/O speeds, but it's certainly compatible, which is all I'd need. After all, Apple even sells a Thunderbolt to Firewire Adapter. I also know that Thunderbolt is not only used for digital video purposes (along with the TB > Firewire option, there exists Thunderbolt External Hard Drives).

There are almost no Thunderbolt to USB 3.0 cables/adapters on the market. I'd think this hardware would be more prevalent given the prominence of USB devices out there. What adapters are available for OS X?

Thunderbolt and USB are quite different protocols, so you can't just use a cable -- it would need to have active electronics in it to convert between the protocols. And that means it would cost a lot more than a cheap commodity USB hub and so no one would buy it -- they'd just get a hub instead. If you're concerned about the power drain, get a powered USB hub.

As a matter of fact "Kanex" the only company I know of that offers "true" adapters put their Thunderbolt to eSATA + USB 3.0 adapter on the market 18 hours ago, at a price point of 69.95$

I also ended up looking for good solutions. Thunderbolt 2 supports 20 Gb/s. So it could provide enough reserves for a real usb 3 hub where every port could finally run 5 Gb/s = 640 MB/s.

As a single SSD already exceeds the speed of a USB 3 connection, we should not put them through a USB 3 Hub bottleneck to not enforce slowing the transfer rates down.

Actually there are some companies that already considered these issues:

• Highpoint offers an Thunderbolt 2 to 4 port USB3 Hub http://www.highpoint-tech.com/USA_new/series_Thunderbolt_Overview.htm, a dock with 2 SAS Ports and a dock with 3 PCI card slots & 4 SSD bays etc.

• Sonnet has a great Dock with an USB 3 HUB & 2 SSD bays http://www.sonnettech.com/product/echo15prothunderboltdock.html and some other good thunderbolt docks with PCIe card slots for USB3 etc.

Other good manufacturers to check out:

• Promise
• OWC
• G-Technology

All in all going for thunderbolt 2 is always on the much more expensive side of the table.

So, I believe the main reason these cables/adapters don't exist is explained in your question, actually. That is, the fact that many, if not all, devices that come with a Thunderbolt port, also already have one or more USB 3.0 ports.

If your primary concern is simply power draw on the bus, I'd recommend simply buying a powered USB 3.0 hub.