Best PCI extenders

I'm trying to consolidate my two GPUs onto one moboard, and since they don't quite fit I need an extender cable.
Everything I find on Amazon is like 3.5 stars with at least one person complaining about ruining their moboard with it.
What do you recommend to use ? I have a MSI 970 Gaming board with a r9 380 and an r9 380x card.
Thanks!