If T-Mobile's recently reviewed T-Mobile Rocket 3.0 4G Laptop Stick doesn't have what you want, you might want to consider the USBConnect Force 4G modem, which AT&T announced today.
This is a 4G USB modem that enables a computer to access the Internet via either a 4G or 3G network. Similar to the Laptop Stick, the USBConnect Force 4G also includes a card slot and works as a card reader when coupled with a microSD card (not included). It supports cards of up to 32GB of storage, which is a decent amount in case you want to carry some data on the go.
AT&T says the new modem works with both Macs and PCs and supports tri-band HSPA/HSPA+ (850/1900/2100 MHz) and quad-band EDGE/GPRS (850/900/1800/1900 MHz) and allows for data roaming in more than 200 countries. Staring July 17, it's available at no cost when you sign up for a two-year service; it costs $50 per month for a data cap of 5GB.
You can also get it for $90 with no contract and use it with a prepaid data plan, which costs $15 per day (100MB included), $30 per week (300MB included), or $50 per month (1GB included).
Unlike with the T-Mobile Laptop Stick, which just throttles down the download speed when the data cap is reached, AT&T will charge you extra when you use over the allowance.