Why can't I get a female header from Mouser?

Looking at the SMR voice card BOM there is one item that I can’t buy on mouser.

It’s the Female 1x6 header, 2.54mm

However i’ve been looking and is this not exactly what is needed?
http://au.mouser.com/ProductDetail/Harwin/M20-7820646/?qs=sGAEpiMZZMs%2bGHln7q6pmzlZUuX%2F53qjd9Ri%2bf2usQ4%3D

No, too short pins. These won’t reach the next voicecard or the motherboard when they are stacked.

Something more like this is better…
http://au.mouser.com/ProductDetail/Arduino/A000084/?qs=sGAEpiMZZMs%2bGHln7q6pmzktK14cxvCUpXuzrRcQqkY%3D
(No idea if this exact part will fit though - but they look right)

That was already in the premade cart but i didn’t know what it was for.

Also, the ATMega is out of stock, do you have any suggestions?

Perhaps this one? Seems like a heat resistant version of the usual one…
http://au.mouser.com/ProductDetail/Atmel/ATMEGA328P-PN/?qs=sGAEpiMZZMuRdXZgphLdVp6CTgYjYYeP