I am currently working with TI's TPS61235. I need to put this IC onto a custom PCB for a project, but I cannot find any libraries for PCB designing software for this VQFN-9 layout. Is there anywhere where I can find these weird layouts to design PCBs with?
You do not know how to use a PCB design tool unless you know how to make a part for yourself — what you own owns you, self-sufficiency, and all that jazz.
You should always be familiar enough with your PCB design package to easily create your own parts. How else can you be be absolutely sure that the footprint matches exactly and adjust solder amounts and stuff?
At the end of practically every (not every, but close enough) datasheet, you'll find a good description of the package and the manufacturers recommended layout, including all measurements needed. Often they also describe how big the opening in the solder stencil should be and more.
If you follow those recommendations, you can be reasonably sure that the design can be manufactured properly, with only minor adjustments.