You could try the Ernie Ball Cobalt Skinny Top Heavy Bottom strings (which are for 7-strings), but they'll be more expensive than regular strings. Or you could get a regular pack of strings from gauge 10-52, and then buy another .62 gauge separately (most guitar stores in my area do separate strings for about £1 each).

Cobalt wound 7-string set (10-62): http://www.amazon.co.uk/-/dp/B009XNP2NA
Nickel wound 6-string set (10-52): http://www.amazon.co.uk/-/dp/B0002PBS68
My Current Gear
Gibson Les Paul Standard Faded (Cherry Burst) || Gibson Les Paul Junior (Vintage Sunburst)
Marshall 1987X and 1960AX || Weber Mass 100
Fulltone OCD pedal || Ibanez TS-9 tube screamer || Big Muff Pi with Tone Wicker || Boss AC2