As one of its daily deals, THAT Daily Deal offers this Flux Capacitor Back To The Future T-Shirt in Blue for $6.49 with free shipping. That's $2 under our October mention and the lowest total price we could find for any similar T-shirt by $6. It's available in sizes S to XL. Deal ends April 8.
Note that size XXL is available for an extra 99 cents, and size 3XL for an additional $1.99.