There are alternatives on the extention... With a little handy work with a file you can convert one of the more common magnetic extentions that you can get at the hareware store, Lowes or Home Depot to work in a pinch...
Yes, I did the same thing. Then I realized that I could only use standard hex bits in that extension. The double ended bits that come with the Leatherman, and ride with it in the bit-kit, will only work in the Leatherman extension. But the extension can also use standard hex bits. For me the added versatility was worth buying the Leatherman bit.