"FRP Strip" is at every Home Depot in 8ft sections standing along with all the rest of the moldings and trim at the back of the wood section. Perhaps it can be referenced by vinyl panel molding. These things are used everywhere: restaurants, bathrooms, mobile homes, ... It is the only thing I have found that works successfully and safely to hold the track together. I cut mine using a fine tooth metal hack saw but a sawzall or even jigsaw would do.

You can go to homedepot.com and
type in FRP
and the first hit is the trim piece. Call and make sure they have some in stock. They will even pull it for you waiting up front by the contractor checkout.
Stabilit America FRP Division Bar Moulding - White
8 ft. x 1-3/8 in. x 1/4 in. White PVC FRP/Tile Divider Moulding
Model # 9290XA
Store SKU # 471869
Store SO SKU # 404572
8 ft. x 1-3/8 in. x 1/4 in. PVC FRP Division Bar Moulding
Model # 9290NL
Store SKU # 764507
Store SO SKU # 404572