You don't need an adapter to plug in a TO-99. The pin arrangement is identical you simply need to form and trim the leads. When I do it the can itself is slightly higher off the dip socket than a pdip so if done well you would need 2-4mm above a standard PDIP. (depending on your skill level at forming the leads you might even get it basically the same height as a standard dip since the can is actually shorter than a dip, you just need room to form the leads and not short them to the can)
I'm not endorsing this seller, just using the image as an example of formed leads that fit into the dip socket in a low profile way. There is no need to solder anything, they plug in just like a normal dip but with a little extra care in pin alignment. So the dip socket in the photo would be the one on the PCB, you are not adding an adapter on top of the PCB dip socket.
I have a hand full of LME49720HA's that are not soldered to dip carriers, I simply plug in the TO-99 package into a dip socket on the PCB when I want to test them.
****If you don't have 2mm+ above the top of the dip or have good mechanical skills then please ignore this as it likely wouldn't fit.