Martijn, Simon,

You might try:

 Containerware
2515 N. 35th Ave., Suite G
Phoenix AZ 85099
(602) 278-2000
Ron Franken
Semiconductor handling equipment/
Containers, trays/Molded,
thermoformed parts

Empak
1501 Park Rd.
Chanhassen, MN 55317
(612) 474-5282
(612) 474-53-99
Teflonware, Wafer boats, Cassettes,
Carriers, Chip Trays

Fuzerè Manufacturing Company, Inc.
1237 Birchwood Dr.
Sunnyvale, CA 94089
(408) 734-4743
(408) 734-90-63
Rosanna Zuniga, Sales Associate
Dean Wolff, Sales Engineer
Vacuum formed wafer boxes

This contact information is a little old, but these
have all been good sources for me in the past

Best,

Dean