sheets for Ikea cribs

[chelle]

We recently bought an Ikea crib and are now trying to find sheets. The problem is the crib is a little smaller than average cribs but not small enough for portable crib sheets. I really like the safety sheets (the ones that are like a pillow case). I am wondering if those will work even if the mattress is a little bit smaller than usual. Does anyone have experience or advice to share on this?

thanks.