Genetic screening for L55P or V30M is very easy and accurate to do. It would take my lab (we are not a commercial set-up) about a week. I wouldn't worry about a fat pad biopsy.

Neuropathy can be associated with amyloidogenic proteins other than TTR. The information in this link might give you something to think about and discuss with your neurologist; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3531896/.