2x6pin pci-e to one 8pin pci-e - an annoying problem of mine

My power supplies have many 6pin pci-e cables but usually only two 8 pin cables. I usually prefer cards with one 8 pin and one 6 pin slots hence my problem :(. Is it safe for me to buy a 2x6pin pci-e to one 8pin pci-e adapter or even one 6pin pci-e to one 8pin pci-e adapter?

What do you think whether this is safe or will it burn my house down?

it wont burn the house but it will smell!!
DOnt use this it is for gamers toys!!

Thickness is important for minning. I would ask the seller the AWG of the cable. If your PSU deliver high AMPs, I would use 16 AWG and never would buy cheap cables online (I have melted a few of them trying to save some bucks with cheap cables).