You will need the looser t-shirt with briefs mesh (bulge version) for the bodybuilder from
here for these to show up in your game.
Here are another 16 pairs of undies/pj's for the bodybuilder, consisting of a looser t-shirt and side slashed undies.
They are organised into 4 sets with 4 outfits in each set.
Set 5.
Set 6.
Set 7.
Set 8.
Credits:
Mesh - Marvine and Beosboxboy