Use activated "wand" of prestidigitation. Does oh so many things for only two pounds of platinum! (1kgp)
+1 Masterwork Sex Toys
150gp for an item that gives a +2 circumstance and +1 competence bonus to whatever check is used for sex. +2/+2 is 450gp, etc.
Command-word activated collar of command. 1800gp for the magic, 150gp for the amazing lock, ~50gp to make it 'magically treated', for a total of four pounds of platinum; the command word gives a command to the wearer. For your D/s play. (2kgp)
Continuous unobtrusive fashion accessory of endure elements: 1kgp; deals with most climatic impedances to sex.
oil of grease. The uses should be obvious. 50gp for one, 1800gp for a command-word unlimited flask
Bridle of mount: <_< >_> You saw nothing. 1.8kgp.
Veil of obscuring mist: Command-worded is 1800gp, grants privacy, for those who are into that sort of thing.
Magic marker of light: attention, for those who don't. 1kgp
Arcane Marker: decorate your partner! 1kgp
Pointer of unseen servant: more like unseen molester. 2kgp; just point it at your target and go! (We disclaim all liability for any possible retribution by victims upon the customer)
Pocketwatch of hypnotism: MC fetish ahoy! command word: "you are getting very sleepy..." 1.8kgp
floating disk: better positioning for exotic sex acts. 2kgp
Hat of disguise has been mentioned before. 2kgp
Something of silent image: I'm sure you can come up with something that fits your own kinks better than I... 2kgp
Animated rope: for bondage escapades. 1.8kgp command word
Something of enlarge/reduce person: size fetishes are a real thing, and I'm not even talking about partial resizing here. 1.8kgp command word
Gloves of mage hand could do some things. 1kgp
Bed of Entangling for even more bondage action. 1.8kgp plus the cost of the physical bed.
+1 Masterwork Ejaculating Dildo (create water variant) So realistic! 1200gp! Cums 2 gallons at a go!
Dildo of Urination (create water variant) go go golden showers! 900gp, and it does 2 gallons on command!
And that (incomplete) list only goes up to 1st level SRD spells.