Power Supply-- 6 pin aux cable?

So, hey everyone. So, the PSU in my computer is dead. The problem is, the motherboard in my computer is using a 6 pin auxiliary power cable, which as I've found out today, is very rare in current PSUs. My question is, am I going to be able to purchase a PSU that still has this connection, or do I need to buy a new motherboard and start over? If I can purchase a PSU, links to specific ones would be great. My current PSU is marked at 300 watts, and it always ran fine up until now. Any help would be much appreciated.