FriendlyElec has a range of boards under their NanoPi brand that might fit:

https://www.friendlyelec.com/index.php?route=product/categor...

The NEO Air in particular is a very compact board using an Allwinner chip, which works pretty well under Linux including such niceties as support for the integrated power management chip.

I also recently got a couple of the Space Cats Jeter Nano boards. They’re more on par with the VoCore, performance-wise, but with a lot of GPIOs on more hobbyist-friendly (read: breadboard-ready) connectors.

As others suggested, FriendlyElec has some good offers, then there are the Orange Pi boards (some of which very similar to the FriendlyElec ones to the point they can boot the same image without modifications). Also take a look at Hardkernel and Pine64 boards; the Rock64-2GB may seem more costly at $34.95, but actually is a lot cheaper since it integrates all peripherals and connectors that would be optional on the VoCore2, aside being a lot more powerful. Also take a look at Armbian for a very well supported Debian-Like OS: many manufacturers cease their support for their boards once the newer models are out, while Armbian and DietPi support a lot of models, including old ones, and are well worth helping with a donation.

https://www.friendlyelec.com/index.php?route=product/categor...

http://www.orangepi.org/

https://pine64.com/product/rock64-2gb-single-board-computer/

https://www.hardkernel.com/

https://www.armbian.com/download/?device_support=Supported

https://dietpi.com/#download

Any AllWinner H3 for example (i.e. first hit at Aliexpress: https://nl.aliexpress.com/item/10000299302152.html) or something like a Sipeed Lichee Nano if you want to go smaller. (https://nl.aliexpress.com/item/4001150568609.html)

For a significant performance increase, but at a larger size (still very small): https://nl.aliexpress.com/item/10000379696950.html

Most of the RockChip/AllWinner/MediaTek type things are China ODM anyway, and besides some middleman-markup the SDKs and reference designs are all the same across the board.

If you want a product that is going to last a little longer and is a bit more useful beyond the basic physical specs (like size and I/O), you'll also want to know what bootrom, bootloader, devicetree and register documentation is available. Native in-tree Linux kernel support would be a must as well. At that point you can essentially boot any (low-footprint) distro forever until SoC support is dropped from the kernel (which takes a really long time if the SoC is still in use).

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Updating mostly for my own peace of mind: like most Chinese native manufacturers, they (the SoC manufacturers) generally don't give a crap about other companies, rights or long-term sustainability. I would suspect this is mostly cultural/political and a bit of 'eat or be eaten', not some dunk in the style of "country bad, people bad". This doesn't mean that therefore nobody should use any products anywhere forever, but like the sunxi community for Linux support (https://linux-sunxi.org/Main_Page) you might need to find out if there is enough knowledge and willingness available to you to actually be able to make good use of the products listed. This is why the Pi is so successful, the SoC is fine but Broadcom doesn't allow any public information on how it works and how to program for it; the community and the foundation around the Pi make it possible to make it work long-term regardless, and for any AllWinner/MediaTek/RockChip you'll want to select your parts in a way that gets you a similarly useful ecosystem. Buying a cheap thing and getting an Hello World out of it today is easy, getting a product that doesn't turn into e-waste in a year is a lot harder.

RockPi S is one of the smaller boards around, albeit still quite significantly bigger than vocore (1" vs 1.7" square)