Mine was tight as well, try a good quality penetrating oil a couple of times, on the cable as well as where it attaches to the throttle body, it worked for my situation, hope it helps for you. As far as getting a new one......... dealer.
Spray oil where it threads in to the throttle body, then turn the screw there with long needle nose. Work the screw all the way in and just about all the way out while spraying oil on it. Thats how I got it. My bike was sitting for 2 years,screw was very rusted
I took my bike in today to the dealership to have the TPS reset and the adjuster broke off. It is the cable that actually snapped. Dealer said I have to buy a new throttle body ($175). They don't sell just the adjuster assembly.
I did fix the broken screw. I ended up soldering the 2 pieces back together. I used a brass tube and slid the 2 ends in and hit it with heat and solder then wrapped it in heatshrink. It works now. I also had to hit the threads at the throttle body with some PB Blaster to get it to turn freely.
Note to all on this subject, this is a item that needs to be inspected and serviced at each oil change as it is common for the cable/screw to bind up due to corrosion. spray some oil and work the screw a little. Remember all this screw does is set the Zero TP position for the ECM and then the idle speed. So moving it in or out does not change anything except idle speed 950-1050. (UNLESS YOU HIT THE TP RESET BUTTON IN ONE OF THE SOFTWARE PROGRAMS. SO DON'T DO THAT,) Terry - www.jtsperformance.com