I agree use the bostich stapler that is specifically for 3/8". Try your local rental stores to see if you can find one to rent for the day. If not their, post an ad on craigslist, email hardwood guys etc. You should be able to find one to rent for a day. Worst case, go buy it, install the flooring and return it.

Well... all I gotta say is.... this is why people hire a pro. To install a small amount like 60 sf professionally or even thousands of sf... you would need to buy thousands of dollars worth of tools. It just does not make sense to DIY it sometimes. The knowledge of an experienced floorguy with 30 or 40 years cannot be had in a couple threads on the internet.