either find a way to the underground shop or get to the engineer
the engineer will have ropes and cages while the underground have collars and dildos but there are still some gears and toys that have to be from stocks or luckily find a character have some on...so far that i have seen
(edit) there also a slave option as well where you can get them to wonder around and maybe someone will put the gear on your slave but there a chance that the slave will break free from those that put gears on the slave
so yeah make sure the slave is on a high lvl or otherwise they will escape
