in a backpack or European shoulder bag (murse) as suggested by @Pnklemonade
One more thing... the douche must be in a checked bag, unless you want it to be taken out of the carry on bag and inspected to make sure it's empty of liquids.
Condoms (that now in the era of PrEP are no longer an absolute must have) and lubricant. I don't know how many bottoms walk around with a douche but I'm sure some do.
poppers... if the client likes them he could have them at home or bring them on a trip himself.
Would you buy it?
I also remember @Unicorn asking if someone would be a house were someone was murdered but I can't find it. There's something related at the end of this video.