These are addresses of various international law enforcement agencies, which I have come accross. Many of these addresses I copied from the various countries' official web pages, so they should be current. However, try them at your own risk.
I add to this list regularly, so check back often.

CUSTOMS
Aduana General, Calle 6, esquina a 39, Plaza, Ciudad Habana, 10600, CUBA
Customs Department, Gikondo and Kanombe, BP 718, Kigali, REPUBLIC OF RWANDA
Customs and Excise Department, Caesar Ridge Road, Port Loyola Area, P.O. Box 141, Belize City, BELIZE
Customs & Quarantine Agency, 1501 Central Avenue Tiyan, Barrigada, GUAM 96913
Department of Customs & Excise, Liberation Avenue, Banjul, THE REPUBLIC OF THE GAMBIA
Department of Customs & Excise, P.O. Box 891, Maseru 100, KINGDOM OF LESOTHO
Division of Customs, P.O. Box PS 158, Palikir, Pohnpei FM 96941, FEDERATED STATES OF MICRONESIA
Direccion de Impuestos y Aduanas Nacionales, Carrera 8 No. 6 - 64, Bogota, COLOMBIA
Direction Générale des douanes, BP 506, Ouagadougou 03, BURKINA FASO (West Africa)
Direction Générale des Douanes, S/C du Ministère de l'Economie et des Finances, BP 163 Abidjan, COTE D'IVOIRE
Directorate General of Customs, PO Box 2, Muscat 113, OMAN (Persian Gulf)
Directorate General for Customs and Duties, Jl. Jend. A. Yani/By Pass, Jakarta, INDONESIA
Director of Customs, Private Mail Bag 012, Port Vila, REPUBLIC OF VANUATU
Duana Andorrana, C./ Prat de la Creu, 16; Andorra la Vella, ANDORRA
Ethiopian Customs Authority, P.O. Box 3248, Addis Ababa, ETHIOPIA
HM Customs Department, General Inquires, Box 898 GT, Grand Cayman, BRITISH WEST INDIES
H.M. Customs, Custom House, P.O. Box HM 2084, Hamilton HM HX, BERMUDA
Ministry of Finance, Department of Customs, That Luang Road, Vientiane, LAOS
Ministry of Finance, Economy & Commerce; Department of Customs, P.O.Box 83, Doha, QATAR
Ministry of Finance, General Directorate of Customs, Budejovicka 7, 140 96 Praha 4, CZECH REPUBLIC
National Customs and Excise Office, Mester u. 7, Budapest H-1095, REPUBLIC OF HUNGARY
New Zealand Customs Service, The Customhouse, 17-21 Whitmore Street, Box 2218, Wellington, NEW ZEALAND
Palau Customs, PO Box 4405, Koror, REPUBLIC OF PALAU 96940
Romanian General Customs Department, Str. Matei Millo nr. 13, Bucuresti 707041, ROMANIA
South African Revenue Service, Customs & Excise, Private Bag X47, Pretoria 0001, SOUTH AFRICA
Zambia Revenue Authority, Customs & Excise, Revenue House, Kabwe Roundabout, PO Box 35710, Lusaka, ZAMBIA

INTERNATIONAL LAW ENFORCEMENT
FSM Postal Inspection Service, PO Box 1376, Kolonia Pohnpei FM 96941, FEDERATED STATES OF MICRONESIA
Inspector General of Police - Sindh, Central Police Office, I.I. Chundrigar Road, Karachi, PAKSITAN
Israeli border guard, hahashmonaim St., lod 72108, ISRAEL
Guyana Police Force, Eve Leary, Kingston, Georgetown, GUYANA.
Guardia Urbana de Barcelona, Guàrdia Urbana 3, 08004 - Barcelona, SPAIN
Ministry of Justice and Public Order, Police Headquarters, Stores Section, Nicosia, REPUBLIC OF CYPRUS
Police Headquarters, Belmopan, BELIZE
Police Technical Centre, PL 20, Kaanantie 4, 00561 Helsinki, FINLAND
Port of Liverpool Police, Police Headquarters, Maritime Centre, Royal Seaforth Dock, Liverpool L21 1JD, UNITED KINGDOM
Royal Cayman Islands Police, PO Box 909, Grand Cayman, CAYMAN ISLANDS (British West Indies)
South African Police, Private Bag X254, Pretoria 0001, SOUTH AFRICA
The St. George Hospital, Security Service, Belgrave St., Kogarah NSW 2217, AUSTRALIA
****Teaching Hospital of the University of NSW. Their patch reads "Special Constable"****

AMERICAN & CANADIAN LAW ENFORCEMENT
Public Works Department, Parks and Open Space Division, Park Police, 2000 Portage Avenue, Winnipeg, Manitoba R3J 0K1
Regional Constable Service, Postal Bag 1006, Bonnyville, Alberta T9N 2J7
U.S. Soldiers' and Airmen's Home, Police Department, 3700 North Capitol Street, NW, Washington, DC 20317 1