I bought both metal and polyurethane (sp?) years ago from
Robt Berthold Jr/Delaware Valley College/Doylestown PA 18901
(he makes them himself!) but  in retrospect I could have done
better if purchased from any of the following (ask 4 free cat):
 
 1 Brushy Mt Bee Farm 610 Bethany Church Rd Moravian Falls NC 28654 usa
  1-800-beeswax
 2 Mann Lake Ltd County Rd 40 & 1st St Hackensack MN 56452 usa
 3 Betterbee Inc RR4 Box 4070 Greenwich NY 12843
 4 Glorybee Pob2744 Eugene OR 97402 - 800/465-7923
 5 Lapp's Bee Supply 500 So Main St Reeseveille WI 53579 - 800/321-1960
 
Incidentally, you can see Berthold in operation in Coggshall/Morse's
book, BEESWAX: Production, Harvesting, Processing & Products
(Wicwas Press, Ithaca NY 14850, 1984, 192pp, soft).
 
Bonne chance.
 
Jack the B-man Ellicott City MD usa