These are the additional cables you might need to purchase if your equipment is not within the standard range of a Promethean board along with a few local stores where you can purchase.  You can always try Amazon for these parts if you have the time to wait.

   Power Cable 15 Foot IEC-IEC connector with female end

   15 Foot USB A to B Cable

   15 Foot High Resolution VGA Cable Male to Male

Here are a few local places where you can pickup the parts.

Industrial Electronics1353 Mookaula Street
Honolulu, HI 96817-4308(808) 847-4300 ‎

Bestbuy
478 Alakawa St
Honolulu, HI 96817
(808) 531-2100

or

98-051 Kamehameha Hwy
Aiea, HI 96701 
(808) 485-6940

IC Supplies
2978 Ualena St # 1
Honolulu, HI 96819-5106
(808) 839-1966

RadioShack