Throttle cable

I've read a few threads and articles about replacement throttle cables being shorter than the original, limiting throttle travel and affecting idle speed.
Does anyone have a recommendation as to where I can source a cable of the correct length?
The replacement I already have was from David Silver, but it doesn't feel right.
Thanks.

I had this problem with a Dave Silver cable and which was supposed to be a genuine Honda replacement. The solution that I found was to loosen the silver cap at the carburetor end and then remove a few millimetres of the spiral tubing that encases the cable. You will also need to remove the same amount of the black outer cable. Refit the silver cap and fit to the carburetor. You may have to experiment with the amount to remove, but five mill is a good start. This worked for me, so good luck.

Thanks Spey.
I did as you suggested and it seems to have done the trick!