If not for its annoyingly bulky design and slightly expensive price, the Toshiba Encore 8 would be your best option for a small Windows 8.1 tablet. As it stands, the Dell Venue 8 Pro is similarly priced, but thinner and lighter.
The Encore 8 features microSD storage and something few tablets — including the Venue 8 Pro — have: Micro-HDMI. As a full Windows 8.1 system, the Encore 8 runs all Windows legacy programs. That is, as long as you can find space. The tablet comes in both 32GB (for AU$399) and 64GB (AU$459) configurations, but honestly, neither size is large enough to comfortably install more than a few large programs. Thank goodness for built-in storage expansion.
The lack of a keyboard/touch pad accessory means you'll want to stay away from the desktop interface as attempting to use your fingers to navigate a UI that was designed with a mouse in mind is frustrating, to say the least. Luckily the tablet is great in Metro.