Well with as many people on here who cosplay, I'm sure you will have no problem finding someone who wouldn't mind lending you their sewing skills. I would, but I don't have any. I'm trying to learn, but haven't quite got it down yet.
But, yeah, I say you should go for it. The younger Eureka would be really cute, and if you found some nice headgear, it's totally meant to be, maaan.....*slips off into daydreamy haze*
Wait.....what was I talking about........oh, yeah....Tigers, man....
I mean, *cough,cough* Eureka costume. Yeah, you should go for it.
And, if nothing else, there is no shame in having a parent help you sew, heh Plenty of people do that....*points to self*