Why would a sheet made for a standard sized baby crib mattress fit a portable or mini sized crib mattress? They are two different products. So a quick fly-by "buy the correct sized sheets" post before I go on to use this particular post again for yet another 'new' post on a completely different topic. :)
Here is what you need to remember and repeat to yourself - your crib is not 'standard' it's mini. This means your mattress, pads, crib sheets and bedding all need to fit to the mini 38 X 24 size (or whatever the size of your particular brand and model of mini or portable crib is).
Searching for sheets: Make sure you search for mini crib sheets
I personally bought the Luvable Friends brand (2) - here and one of these because I loved the argyle beige design. These two links fit the 5" mini crib mattress I purchased.
The bedding set I chose is this adorable little jungle animal set: Dream On Safari Animals Portable Crib Set
The sheet that comes with the set fits the original thin pad the crib comes with but if you opt for a different mattress you have to buy accordingly.
*NOTE: When I first bought this crib I substituted a thicker mattress at the time because the baby was an infant and not only did I want the support of a good mattress, but leaning over the rail to carefully and quietly place a sleeping infant is almost impossible when the mattress is even further down than the length of your arms. Leaning over the rail, I couldn't even reach the mattress easily so the baby would wake every time he was laid down. We invested in a nice mattress at the time which raised the tiny baby up a couple more inches, which was high enough so I could easily get him in and out of the crib easily and not wake him by jolting or jostling as I tried to reach the mattress with a sleeping infant in my hands.
If you also are doing that - be sure that once the baby can start to sit up and stand, you need to only use the 1" mattress that comes with the crib. You need the rail height for safety. When the baby is pulling themselves to a standing position - OUT comes any other mattress and only use the standard!
If you like any of the ideas on my page, please consider using my affiliate link to make any purchases you have planned through Amazon. (Even if it's something not related to this page). Thanks! Budget at Amazon