Single Slot Mid Range Graphics card under 18cm

I'm looking for a decent mid to high end graphics card that is shorter than 18cm and has a single slot cooler. I'm building a mini-itx pc with a Chieftec BT-02 case, it only has room for a single pci-e gpu cooler with a maximum size of 18cm.

Have currently bought a sapphire hd 6770 (1gb) dual slot which I attempted to fit in the case (Bought it thinking I could squeeze it in, the PCB fits by mere millimeters with the cooler removed, however the original cooler overhangs the back of the card by about another 5cm and doesn't fit, its also dual slot and collides with the PSU)

Can anyone recommend either a single slot cooler that works for the 6770 or another graphics card of similar specs that would fit? Have been searching for awhile now and can find neither. Will import parts if they are only available abroad (Live in UK)

Thanks.

Specs:

Zotac Z68ITX-A-E Motherboard
i5 2600k
8gb ddr3 1600mhz cr7
Generic Silverstone 450 watt SFX PSU (can be upgraded)