This item was pretty much the result of Shivamuffin creating the Bra of Holding and some of the comments therein.
Full Item Description
Generally crafted in the form of common undergarments, these magical pieces of clothing actually contain extradimensional spaces of a moderate size, allowing items to be secreted away within them, as well as the body parts generally involved with said undergarments. This is of benefit to several groups of people; those who want a secure location to sequester small goods can readily stash them in the garment, as can those who are stashing items for more nefarious reasons. Given the likelihood of being searched in ‘intimate’ locations in many countries, these can be a very effective way to smuggle contraband into a location. Moreover, those unaware of the item’s nature are unlikely to find the stashed items even if it is checked.
A second and more unorthodox use of the item is as an aid in concealing one’s gender. Given the right fitting, and the decision to do so, the garments can be used to conceal the most noticeable sexual characteristics of a person - hiding a woman’s breasts in the pocket space, or a male’s genitalia, thus greatly facilitating the ability to disguise oneself as the opposite gender.
Originally created by a brother-sister duo of mage-thieves to facilitate in their sleight-of-hand thefts, the two also quickly discovered that they could use them to change their looks, making it possible to commit absurdly daring thefts and walk around in public without a qualm, leaving those fooled by them to hunt for a younger boy and girl rather than the mature and endowed rogues responsible. Eventually, once they had more than enough funds to live comfortably to live out their lives, the two quietly departed their old hunting grounds and set up shop in a distant city, selling their marvelous line of clothing to petty rogues and those paranoid of theft alike. Many others have since imitated the items, leading to many minor variants, such as girdles which allow for a trim figure but easy breathing, or gloves which hide overlarge and unsightly hands and fingers in smaller, more attractively-sized gloves, although the odd articulation of the fingers as the tips vanish into the extradimensional space at the fingertips of the gloves is usually a giveaway.
These items simply function as minor extradimensional pockets; most hold only a small amount, perhaps a cubic foot, more than sufficient for the needs of most. Larger pockets spaces do exist, of course; the girdles commonly are an example of such. Used for gender disguise, they provide a significant bonus to the disguise check, and can provide a limited bonus on other forms of disguise, depending upon the clothing in question, at the GM’s discretion.
Clothing of Concealment
Sometimes, you just need to stash something away - some spare cash, a holdout weapon, your gender…