John Meadows has a supplement called MD’s Ultimate Glucose Disposal Agent, it is $30 for 90 servings worth if you are looking for somethings along those lines. Not claiming that it is the same as Receptormax, but could be worth looking into.
I think you are on the right track, as I say ignore my diet advice while you are following Nate’s, do your walking and you can always add the alternating reverse lunge and pushups part of the PLP split into parts before meals, this too will help a little and prevent fatigue build up. Do 5 reps per leg and 5 pushups rather than as many as you can, the results will add up more than logic would suggest.