You Want the Corpse Creature Template
The template corpse creature (BoVD 185) meets your criteria. It's an unupdated D&D 3.0 template, however, and corpse creatures "cannot be the result of a simple animate dead spell, but could arise from a create undead or create greater undead spell, as undead of their equivalent Hit Dice," so getting corpse creature stirges into the hands of a lower-level vampire necromancer might be problematic.
"What's a corpse stirge do?"
A corpse stirge pretty much does everything a stirge does but with a layer of undead on top. It gains a natural attack (which doesn't mean much to such a low Strength Tiny creature), gains darkvision 60 ft., undead traits (which is a big deal), increased Strength, and lowered Dexterity. You're going to have to work out the stirge's new attack bonuses and other statistics using Table 1-1 on PH 8, but the Strength increase makes the corpse stirge quite a bit more frightening to low-level PCs because of the stirge's massive racial bonus to grapple checks with its attach special ability.
The natural attack granted by the corpse creature template does give the corpse stirge an option it didn't have before: instead of using the touch attack and subsequent attach ability (which starts a grapple), it can slam folks; damage will be miniscule (1 point of damage on average). At the DM's option a corpse stirge's slam can be its primary natural attack. On a full attack the corpse stirge makes a slam first and then its secondary natural attack--the touch attack (at a -5 penalty for a secondary natural attack)--that, if successful, activates its attach special ability. If intent on using the stirge's new slam, it's probably not a good idea to make the slam the secondary natural attack, as that means that attack roll (at -5 because its secondary) is only made if the touch attack missed as the grapple from the attach special ability starts the stirge grappling. I'd keep the touch attack as the primary natural attack and not worry about the slam; the corpse stirge will probably be better off trying to win an opposed grapple check to damage its opponent than trying to attack his grappled opponent with its slam at -4 (PH 156).
A typical corpse stirge is Challenge Rating 1 (see Rounding Fractions on PH 304).
Acquiring the Create Undead Spell
A Blighter 5 (CD 23-6) with Wisdom 20 can cast the 5th-level spell create undead [necro] (PH 215). That blighter could assist a 9th-level caster possessing the feat Craft Scepter (LE 8) (a scepter is a wand holding up to 2 up-to-7th-level spells instead of the 1 up-to-4th-level spell of a wand) craft a scepter of create undead (5th-level spell at caster level 5) with a market price of 21,250 gp with each of the 50 charges capable of making a 1-HD undead (only 425 gp per charge in case you just need to explain a handful of corpse striges or want to buy the vampire a used scepter (c.f. Used Wands on MIC 227)).
(As an aside, it's sad the blighter must advance his caster level beyond the limits of the blighter class via a prestige class, magic items, or natural spellcasting to create even the weakest undead available via the spell create undead as the spell’s presented in the Player’s Handbook. Maybe his bitterness at not being able to use his spells as intended is why he’s helping a vampire make corpse creature stirges?)
A Ridiculous (Free) Alternative
The template multiheaded (SS 124-6) can be applied to a magical beast; this adds 2 HD and makes stirges hilarious. In addition, the template beast of Xvim (Mon 85-6) can be applied to a magical beast; this adds another 1 HD and grants the creature the beast of Xvim template's supernatural ability feed, allowing it to increase its HD via feasting on the dead. A multiheaded (2 heads) stirge of Xvim has 5 HD after using the feed ability once, making it eligible for the template monstrous vampire (Gh 166-67). (The vampire's supernatural ability create spawn (MM 252) sadly only creates vampire spawn (MM 253-4) if the creature is less than 5 HD.)
This turns the stirge into an awesome CR 5 (rounded down) Tiny 2-headed, glowing-green-eyed 5-HD vampire batsquito that's eligible for class levels with its Intelligence of 5. None of the listed templates were updated to D&D 3.5, however.
"Wow, That Was a Big d20 Boom"
Behemoth3 released Masters and Minions Horde Book 1: A Swarm of Stirges in 2004. I don't own it, and I'm not associated with Behemoth3, but, y'know, if you're, like, into stirges, someone's got your back.