I got my 70 chain at Rural King when they had a mail in rebate with 10 or 15% off everything in the store. I think I paid $60 for 16 ft.
What I do is use chain at the rear of the tractor. To tighten, I pull forward. The chain stops me where I want it to be. Then I use 2 DOT approved straps to pull the tractor forward. 2 more straps to pull forward at a 45 degree angle and 2 more straps at the rear of the tractor to pull at 45 degrees backward. Works for me.