Best places to buy 21/41 gear and chain

[Billy Boy]

Hi everyone, after installing my mpi 180 trail kit on my ltxse, a little clutch work, primary is machined for overdrive, I hit 109 on my gps. I would like to go a little faster on the lakes and maybe get better fuel mileage on the trail. I'm down to 10 or 11 mpg now. 120 mph should be good, so I need 11 more mph. I see the 21/41 gears seem to be very popular on here. Can anyone tell me the best place to get this set up? I know I could go to the dealer, that is one option. Thanks.