Hi,
According to this link the part number is JVC 964TDP7255-778 and it is ''discontinued''. (Scroll down to Sub Woofer Cable).
Searching for this part number brings no positive results. All results say discontinued.
http://www.pacparts.com/model.cfm?mfg=jvc&model_id=THM303&action=list_part&back=0&mode=auto
If you click on this link it says to ''Use Jvc-Qam0381-002 ''
http://www.pacparts.com/part.cfm?sku=964TDP7255-778
When you search for this number there are two results which still have stock.
https://www.amazon.com/JVC-OEM-QAM0381-002-QAM0381002-CABLE/dp/B004GIZ8KE
http://www.rakuten.com/prod/jvc-qam0381-002-system-cable/229955722.html
I hope that it is the correct one and that this will be of some help.