The best advice I have to give is this: don't shop in the diaper bag aisle. Honestly? The only thing that differentiates diaper bags from the other bags in our lives are the things that come in them (bottle coolers, accessory baglets) and you can get those elsewhere. Get yourself a plain messenger bag - they work really well and, unlike most diaper bags, they'll stay on your shoulder when you're juggling an infant, your housekeys, and your laptop case. In fact, if you have a small enough laptop and a large enough bag, it can serve as both a diaper bag and a laptop case. (Me, I'm running a 17" widescreen - ain't no way it's covering both.)
Ok, so the messenger bag wasn't enough for me. I had to take it one step further.
Some sources for Stargate patches:
A gazillion SGC+ uniform patches from patchgeeks.com (how can you argue with a site that's got geek in its name??!)
Ok, so they can't spell, but I love that they feel the need to specify which galaxy they're shipping from: Intergalactic Trading
And for those who are feeling more diabolically geeky and are on the other side of the pond: Jaffa patches
