I'll give you a bit of a peek behind the curtain that might explain why the style of shirts you are looking for are hard to come by.

Most t-shirt sellers are using services like Printful and Printify to fulfill their orders via direct-to-garment printing.

Printful does not have baby tees available as shirt blanks at all. Printify does, but take a look at the differences here:

Baby tees start at $25.33 just for the shirt blank, without any print on them at all.

Additionally, they only have 2 providers who can print on them and only come in 4 colors: White, Black, Sand, and Pink.

For something that is feminine, but not quite so spendy for the shirt blank, Printify has a "Softstyle" tee starting at only $9.34 before printing.

It's also available from 10 providers, instead of just 2, and comes in a wider range of sizes and colors. Just doesn't show the midriff. 😉 Could always be modified to do so by the buyer, I am sure.

Compare both of these with the unisex shirts EVERYONE has available. The blanks start at only $8.61 and have far more available options:

22 providers and over 70 color options? Yeah... That's why t-shirt designers default to this option.