Yeah I would go with either an Exmark or Honda commercial mower, but Toro would be good, too. You would probably want the self-propel option, because commercial mowers can be very heavy. But you should still be able to push it into the truck. Here are some examples of the weight. The ones with self-propel weigh more than the push models, but the push ones are still heavy so you should think about the self-propel.
Honda:
Commercial HRC push- 100 lbs.
Commercial HRC self-propel- 127 lbs.
*To give you a comparison, Honda's residential mower (HRR) is around 80 lbs.
Exmark:
Commercial 21: Both models are self-propel to my knowledge.
S-Series- 112 lbs.
X-Series- 112 lbs.