Instead, I found several vendors on Etsy that email you a pdf and/or jpg of the design and then you print out as many invitations as you need on whatever paper you want. This seemed like a great deal because the design was just $15 - putting each invitation at 50 cents. My research told me I couldn't beat that.
I went with Bella's Boutique Design for her awesome nautical design, size, price and speediness. You could order them in a 5x7 or 4x6 size, which not all shops offered. Bella also touts she can get most orders emailed to you in just 24 hours; mine were in my inbox in less than 12. I opened the files, they looked great and printed perfectly. I did have access to the color printer, card stock and paper cutter at my office, which I'm sure helped polish the look. I had never ordered downloadable invitations before so I was a little nervous they wouldn't turn out well. Not at all!
I do have to take credit for the little alarm clocks you see in the photo. The shower is also an "Around the Clock" theme so I figured a little clipart would compliment the invitations just fine.