I got these single eye shadows from Elf and thought I'd review them for you.
They are in 26mm pans so they will fit into a Mac Eyeshadow palette.
You can get small 4 pan palettes from the website that you can put custom blushes and lip pans into too.
The quality is so good on these, the colour payoff is strong and they are really cheap €1.70/£1.50/$1.00.
I have four, here are the swatches.
Ivory is a really good highlight and inner eye corner colour.
The only small downside to these is fallout and that Elf don't have more colours in them!!!