I think as small as you can get is the best. The 27-gauge is fine. Seems like I even used 29-gauge. Make sure you get the short needles. I remember my first shot of Pegysys -- the pharmacy gave me 25-gauge and 1" long -- holy cow, that was rough. It wasn't until I checked with the forum here that I found out what to tell the pharmacist.
What week of treatment are you starting the neup?
You could probably use diabetic insulin syringes
Pegasys prefilled syringes are 27-gauge 1/2 inch needles. Neupogen prefilled syringes are also 27-gauge 1/2 needles.