For in story purposes you could do that you either chemically create the creep (look for something like a sticky floor trap kind of thing or spell) or that when you summoned the zergling a portion of creep came with it slowly starting the process to spread it.
In the long run though I think it would be an interesting idea if your summoner became the Zerg Overmind, creating the race and then becoming one with the race at the same time. If I could grab my UM and APG I'd help out some in feat/power choices to help with that.
Think of Creep as skin, flesh and veins between the zerg "buildings", which are the organs of the giant zerg body that is the hive. That's why there is no creep on it's own - it needs a hive it belongs to.
Having a small spot of creep is like having a small spot of human skin - it's dead.
Who are you? I'm not being Volon here, I just want to know your angle: Are you trying to do this as a player or GM?
And is anyone else getting Codex Alera flashbacks? Vord! (that's not "Word!" with funny spelling)
I'm trying this as a player. Using eidolon blood as a basis for rapid evolution of the Zerg.
I say that your best bet is to work with the GM. No matter how many books Paizo releases, they probably won't offer you the perfect solution for what you want.
But one thing I can recommend is the broodmaster archetype for the summoner. Instead of one big eidolon, they get many smaller ones. That makes a lot of sense for the Swarm - they don't have the most powerful creatures, but they are legion. You can find it in Ultimate Magic (or in the PRD).
You could also ask for a flavour change: If you use buff spells, there is a physical manifestation of it in the form of Creep (creep works like the haste spell, anyway) that is constantly spreading around you and empowering your brood.
The building aspect will probably not be a big deal, since adventurers tend to move around (much like Sarah will apparently operate in Heart of the Swarm).