Where can I get a smaller (size) video card?

I recently purchased this: Acer Black AX3400G-U4802 Desktop PC with AMD Athlon II X2 Dual-Core 255 Processor and Windows 7 Home Premium (64-bit) (http://www.walmart.com/ip/Acer-AX3400G-U4802/15686808). I bought a 9600 GSO PCI-E 2.0 x 16 since there was a PCI-E x16 expansion port in the tower. However, the tower is smaller than norm so the card was too big size-wise. What should I be looking at in terms of size? I want to spend between $50 - $75, and don't need anything super high-end or anything.